The body prefers a relatively stable temperature of 97.7– 99.5°F (36.5–37.5°C). Whether shivering from the cold or sweating from the heat, the body is attempting to maintain the core temperature close to 98.6° Fahrenheit. This process is called thermoregulation.
Early studies concluded we have a thermal circuit-breaker (also known as the Central Governor) that trips when we get too hot, and those studies limited sports research for some time. Subsequent studies, however, have shown that trained athletes are able to push their core temperatures higher than sedentary people. In fact, that thermal circuit-breaker seems to be triggered more by a perception of heat rather than the temperature itself, and our perceptions of heat are blunted by the mere presence of competition.
The first event of the 2016 UCI Road World Championships in Qatar was the women’s team time trial, a mid-afternoon 40-kilometer cycling race in temperatures averaging 98.4°Fahrenheit (36.9 C). Three cyclists from one of the teams swallowed ingestible core-temperature-sensing thermometer pills with their breakfast as part of a study to investigate the effects of hot-weather, competitive exercise. The researchers found that the three women had peak temperatures during the race ranging from 105.4° to 106.7°F (40.8 to 41.5 C).
It had long been accepted that if you ask an athlete to exercise for as long as they can in a hot environment, they’d quit when their core temperature reached somewhere around 104°F (40 degrees Celsius). These three cyclists all reached higher temperatures than the perceived threshold, yet they hadn’t collapsed. They won a medal.
Exercise produces heat that the body must eliminate so that it can maintain a stable core temperature and prevent over-heating. Exercising in hot conditions is even more challenging since the primary source of eliminating heat through sweating is less effective in hot and humid environments. If the body sweats so much that it depletes itself of fluids and salts, there’s nothing left to sustain the evaporation process. And when the process of regulating ceases, body temperature soars causing heat illnesses or even heatstroke.
Studies find that after a period of heat training/acclimatization, however, our bodies are able to produce more sweat and earlier, overall core temperature and blood lactate is reduced, blood plasma volume increases creating better cardiovascular fitness, skeletal muscle force increases, and we get better while training in a wider range of temperatures including cold weather. In fact, purposely training in the heat may be more beneficial than altitude training since we adapt more quickly to heat stress than to hypoxia (oxygen deprivation).
While many of these benefits can be obtained by simply living in the heat, exercising in heat speeds up the process. And there’s ways to mimic heat training, in case your next race is in a hotter climate than where you live.
This post discusses key points regarding the athlete’s response to heat; hydration, dehydration and sweat; heat versus altitude acclimatization; pre-cooling methodologies; and thermotolerance training techniques and guidelines.
Brain: an almond-sized portion of the brain (the hypothalamus) is hyper-sensitive to changes in core temperature. If the core increases by even one degree, it reacts by opening blood vessels near the skin and routing blood to the periphery where it can cool. In an environment where the air, humidity, wind and sun feels warmer than 99.5°, the brain will limit contraction of the muscles as a way of telling the body to stop generating so much heat. This forces the athlete to slow down before becoming too hot.
Skin: As warm blood reaches the skin, pores expand and you begin to perspire. The sweat evaporates and cools the blood directly underneath. If the air is warmer than your core temperature, sweat is actually wasted and your condition worsens since the sweat fails to cool but contributes to dehydration instead. Pouring cold water onto the skin will help, but only temporarily.
Heart: When blood is over 98.6°, and more blood is being pumped near the skin for cooling, the heart is working harder, beating faster. Perceived effort will increase and recovery will be longer.
Of Special Note: Data froma multidecade study of 2,300 Finnish men found that those who hit the sauna four or more times a week were only a third as likely to develop dementia or Alzheimer’s compared with those who took just one sauna a week.
In a 2017 study from Qatar, participants showed a 17 percent boost in muscle strength after 11 days of sitting in a heat chamber at roughly 120 degrees for an hour at a time. The technique might be particularly relevant for injured athletes or those recovering from surgery as a way to maintain their muscles when they can’t exercise.(Alex Hutchinson, OutsideOnline).
Dehydration and Sweat
While fluid plays a role in heat, it is actually more minimal than we may realize. When athletes are allowed to pace themselves in trials where they are limited to small volumes of fluid or do not drink at all, they reach the same core temperature as when fluids are consumed, but they take longer to finish. It’s not necessarily the fluid ingested that keeps us cool, but the metabolic rate, or how hard we are exercising that affects core temperature. The guiding principle here is to always drink to thirst.
Sweat rate also has nothing to do with the rate we burn fat or calories. An individual’s perspiration rate is mostly dependent on genetic make-up, training, and how the body responds to heat stress.
Some people lose more fluids than others, and men perspire more than women. Testosterone can enhance the sweating response, as will anti-depressant, anti-anxiety, allergy, decongestants, and weight loss medications. Caffeine has a similar effect.
Urine color is determined to be a simple way to assess hydration. Observe urine over the course of a day and notice changes in flow and color. Volume and frequency should be consistent and the color should be lighter, or close to clear, toward the end of the day.
Why It Hurts
Core Temperature = Heat Production vs Heat Loss
Heat is produced when muscles contract and is directly proportional to how fast you are running. Run two times faster, twice as much heat is produced. Consequently, it’s the shorter, more intense races that produce higher core temperatures.
Heat loss depends on evaporation, convection and radiation with the environment being the crucial factor:
– high humidity prevents evaporation,
– high air temperature prevents both evaporation and convection from cooling the body.
Runners learn to push through the pain, but to successfully push through the pain means we must also understand the warning signs that would spell disaster in any given situation.
If our perceptions of heat are blunted by the mere presence of competition among other things, overheating could become the unintended outcome. Know the symptoms of overheating: headache, dizziness, disorientation, nausea.
The Gender Gap
In 2011, VF Corporation, the parent company of Smartwool and The North Face, commissioned a 1,200-person study examining how women and men respond to exercise in hot and cold temperatures.
Their findings show that women run warmer than they perceive. In winter, women’s coldest zones are the backs of the hands, the glutes, outer arms, and kneecaps. Women’s upper backs, calves, collarbones, and pelvis emit more heat during stop-and-go cold-climate activities, such as skiing. During hot-weather exercise, women’s legs are markedly cooler than their upper bodies, while men are more evenly balanced. Women’s feet are always colder than men’s, regardless of the outside temperature.
Acclimatization and Thermotolerance
Thermotolerance is the end result of a successful program of heat acclimatization, where an athlete trains with the specific purpose of making the body functional in a warmer climate to which the athlete is accustomed. (Encylcopedia.com)
Acclimatization methods consist of two types: heat and altitude.
The body undergoes a natural acclimatization to warmer temperatures or higher altitudes, known as passive acclimatization. It is possible to speed up this process through a gradual buildup in training volume, known as active acclimization. While both heat and altitude alone are stresses to the body that will contribute to the acclimatization process, heat or altitude without exercise will not be as effective.
Altitude Acclimatization develops the ability of the athlete to better utilize oxygen, which makes them more effective at sea level competition. At higher altitudes (≥8,000 ft / 2,500 m), the body compensates for the decrease in available oxygen by increasing its production of red blood cells, which transport oxygen through the body. Altitude training will increase oxygen capacity by between 2% and 3% in a period of about three months. Although this benefit will remain for several weeks in an ever-decreasing amount, it will be completely lost within three months of returning to lower altitude.
Note: Altitude training is broken further into three types: “live high/train high,” where the athlete both lives and trains at altitude; “live high/train low,” a regime where the athlete lives at altitude but trains at sea level; and sea-level training, where the reduced oxygen environment of higher altitudes may be replicated through an artificially configured house or training “tent.” The extensive scientific research regarding altitude training confirms that all three methods will enhance sea level performance.
In the Heat Acclimatized athlete, cardiac function improves resulting in increased plasma blood volume accompanied by a 15-25% decrease in heart rate. This means there’s more water in the blood stream that can be used by the sweat glands to produce more sweat. Thinner blood means it can also transfer heat more effectively to the skin. (Note: the systems of the body adapt to heat exposure at varying rates.)
Heat acclimatization also reduces muscle glycogen utilization and post-exercise muscle lactate concentration. Chris Minson, a professor of human physiology at the University of Oregon who studies heat acclimation responses in athletes, has also found that changes to the heart’s left ventricle specifically helps to increase oxygen delivery to the muscles.
Hot and dry environments are different from hot and humid environments (desert vs jungle) – sweat rates being higher in humid environments (the rate of sweating influences thermoregulation). Acclimation is also dependent on the volume of exercise, intensity, and how long the core temperature remains elevated.
In a nutshell, heat acclimatization causes the body to shed fluids sooner by sweating sooner, lowering the core temperature, and making the athlete more comfortable – perception of effort being key to exercising longer (a decrease in ‘perceived exertion’ occurs during the first five days of exercise-heat exposure). An added benefit is that many of these adaptations will be useful even in cool weather training.
The human body is very adaptable to heat, and to corresponding humidity, with the major benefits achieved within 10 to 14 days of beginning a heat training program; most athletes will reach an acclimatization of approximately 75% (defined as an ability to perform to 75% of their top level) within five days. If the athlete is not exposed to warm weather conditions on a regular basis, however, the body will require another acclimatization period. On the bright side, re-acclimatization occurs more rapidly than the initial acclimatization when re-exposed to heat (Weller et al., 2007).
The chart below compares the benefits achieved during heat training as compared to passive acclimatization (no exercise) and exercising in cool conditions.
The Central Governor Effect (and sometimes lack thereof)
In a 2012 study, the negative effects of cycling in 89-degree heat were partly erased when the thermometer in the room was rigged to read 79°F. In other studies, athletes react to hot conditions when their skin temperature is warmer to the feel even though their core temperatures were actually lower. There’s also research that suggests our perception of effort is lower in competition, partly because our attention is focused on the competitors rather than our own pain.
Exercise physiologist, Jo Corbett, and a team at the University of Portsmouth put cyclists through a series of 20k time trials in cool and hot conditions, with and without competition. The cyclists hit higher temperatures during the competition than when they were soloing in the heat, although their ‘perceived’ measurements were the same. ”Thermal sensation” (how hot they felt) was the same, as was “thermal comfort” (how pleasant or unpleasant the heat felt). Racing against a competitor created a disconnect between how hot they were and how hot they felt even though they cycled faster and generated more power during the head-to-head competition in hot conditions.
When athletes in one study were equipped with a small electric heat pad tucked in the pocket of their shirt, they gave up 9 percent sooner even though none of the physiological measurements – blood lactate, core temperature, skin temperature, heart rate, stroke volume, cardiac output, oxygen uptake, ventilation – were different. They simply quit because they felt hot.
This doesn’t change the fact that our bodies undergo significant added stress while exercising in the heat, but it may be useful to know that a great deal of the pain is purely psychological.
The Pre-Cooling Option
Numerous studies have shown that pre-cooling before prolonged exercise in hot temperatures may help sustain intensity and speed, however, definitive conclusions on its effectiveness have not yet been established.
Methods of pre-cooling include whole-body cold water immersion (17-30°C for 30 minutes); cold air exposure; cooling garments; cryotherapy; and internal cooling methods, such as cold beverages, ice slurries, and ice bars.
Some athletes follow the low-tech protocol of simply applying ice packs – to the back of the neck, chest, underarms or between the thighs – with preference to areas with the highest blood flow. Because thermoregulating the brain is essential (and ‘perception’ is everything), ice on the neck significantly relieves perceived heat stress. One study also found a 20% increase in cycling power during an intermittent sprint when ice was placed between the thighs.
Athletes sometimes report feeling heavy or sluggish following whole-body cold water immersion. An alternative is to expose just part of the body to cold water by soaking garments in cold water, or submerging specific active or inactive body parts directly in cold water (such as the hands or legs).
Practicality is a logical consideration when choosing a pre-cooling protocol.
Hampers the performance of sprinters
Better for sports with intermittent sprints
Best for endurance events, triathlons, cycling races or marathons
* Pre-cooling has also been shown to improve performance in lower ambient temperatures.
Make a reduction in skin temperature your major goal;
Aim to pre-cool for 8-30 minutes;
Practice your chosen pre-cooling technique before using it on race day.
Heat Training Protocols
Heat training approaches can be as simple as running outside when it’s hot; using the thermostat to create a hot environment indoors; wearing extra clothing that is certain to make you run hot; or spend time in a sauna, hot bath or hot tub post-workout.
Because heat is an added stress, however, any protocol that separates the stress of heat from the workout allows the quality of the workout to be preserved. When training in heat, training volume and/or intensity would be reduced initially as the body adapts.
A 2015 study shows that using a six-day, 104°F post-run hot tub protocol was effective at triggering heat adaptation, including a 4.9% improvement in 5k time in 91° heat. The advantage of using a sauna or hot tub is that it prolongs the amount of time the core temperature remains elevated (going for a run in normal conditions elevates the core temperature, and the hot tub prolongs this period of time).
Here’s a graph that shows core temperature (38.0 C is 100.4 F; 40 C is 104 F) at the end of a 40-minute hot run before and after the hot tub protocol:
Heat Training Guidelines
The most successful heat training programs will follow a progression:
Training volume and training intensity are reduced initially.
Both volume and intensity are increased as the athlete begins to adapt.
Exercise extreme care to ensure proper hydration is maintained at all times – before, during and after training sessions. When dehydration or salt deficits exist, cardiovascular and thermoregulatory responses may be negatively affected, and the theoretical risk of heat illness increases.
Increase the sodium in your diet for the first few days. Sodium helps the body retain necessary fluid for temperature regulation.
Take breaks to allow the body time to cool down.
Ultra running coach Jason Koop says, “at a certain level, you have to compromise training quality for the heat acclimation. Acclimating to the heat is additional stress [on the body], just like more miles or intervals, so you can’t simply pile it on. Something on the training side has to give.”
If you want to incorporate heat into your workouts, here’s how Koop recommends doing it safely.
1. First, pick a protocol (sauna, hot bath, or exercising in the heat) that minimizes the impact on training, both physically and logistically.
2. Koop most commonly recommends that his athletes use a dry sauna immediately after running. “It doesn’t impact training nearly as much as running in the heat, and the effects are similarly positive,” he says. He often tells his athletes to not drink water during these sessions to enhance the effect. Koop recommends spending 20-to-30-minutes in the sauna, depending on tolerance.
3. Koop says that when he has his athletes exercise in the heat—either naturally or by wearing extra clothing to simulate the experience—it will be on a long, slow day for 60 to 90 minutes. The time completely depends on the athlete’s tolerance and previous experience. But he stresses to not do this on a recovery day, because heat training is an added stress on the body. Koop recommends drinking 30 to 40 ounces of an electrolyte drink per hour during these sessions And for safety, he advises using low-traffic sidewalks and bike paths—not trails.
4. Despite the benefits of heat training, Koop reminds his athletes that running in the heat is extremely difficult and usually replaces a hard day. “You are substituting one potential gain for another one,” he says. In other words, use it carefully.
Know the risk factors of heat illness:
●Strenuous exercise in high ambient temperature and humidity
●Lack of acclimatization
●Poor physical fitness
●External load, including clothing, equipment, and protective gear
This post is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding medical questions, concerns, and before beginning any new training regimen.
Choose the Proper Equipment A large nail clipper works well. Avoid scissors or knives. An emery board is important for filing down thick nails or smoothing rough nail edges, and a pumice will aid in reducing calluses.
Wet or Dry? Trim your toenails when they are dry. Dry toenails are less likely to bend or tear when you cut them. For thicker toenails, cutting is easier after a shower.
Use a Straight Cut
Trim the nail straight across using two cuts – the first cut should be with the clippers slightly off the side of the nail to create the straight edge; the second cut removes the rest of the nail following the line of the straight cut. Smooth the edges with an emery board.
Don’t cut in a curved pattern or cut too short, as this may lead to ingrown toenails.
A good standard is that you should be able to run your finger across the top edge of your toe and barely feel the toenail. Trim often to maintain this length; approximately every 4-5 weeks in cool weather, and every 2-3 weeks in warmer weather.
Why it hurts.
Black Toenails: A subungual hematoma (bruising) under the nail that is generally caused by trauma resulting in a collection of blood underneath the nail. This collection not only causes the nail to become discolored, it also generates a tremendous amount of pressure, and can cause intense pain.
Black toenails may eventually lead to the loss of the entire nail (it will grow back). If there is pain or a foul smell (indicating an infection), seek medical treatment right away.
Fix it: the easy answer is to keep toenails short. Trauma occurs from the toenail hitting the end of the shoe.
Some suggested remedies include wearing larger shoes. While it is important that your shoes aren’t too short or small, shoes that are too large will cause other problems, such as blisters. Shoes that feature a larger toe box may help alleviate trauma to the nails, but the best place to start is to simply keep nails short.
If there are no underlying conditions, such as an infection, the nail will eventually fall off, a new nail emerges, and the injury heals without intervention.
It is possible to have a black toenail that is relatively painless. However, if pain is persistent, the hematoma can be drained to relieve the pain and pressure. Visit the doctor earlier rather than later to ensure the new nail regrows normally.
Brave runners may choose to drain the hematoma themselves. Jeff Galloway’s website contains step-by-step instructions for this procedure.
Some runners, such as ultra trail runners, may continue to be plagued by painful black toenails even after taking every precaution. Occasionally these runners will have their toenails surgically removed.
Note: black toenails can also be caused by a fungal infection, common in immuno-compromised patients, or they may indicate underlying melanoma (a malignant tumor consisting of dark-pigmented cells called melanocytes). In the case of an underlying infection, there may be pain associated with redness, swelling, foul odor, and discharge.
Thick toenails: nails can thicken with age, because of a fungus, infection, or trauma. Any alteration to the nail plate, nail bed, or root of the nail can result in thickening. This damage may be temporary or permanent, depending on the cause.
Runners may experience thickening of a nail from the repetitive pressure or continual striking of the nail against the shoe (trauma) causing it to separate from the nail bed.
Thickened toenails may or may not be painful, but they are difficult to cut, and they can increase one’s susceptibility to infection.
Fix it: use an emery board or nail file to immediately reduce the thickness of the toenail. This is the first and easiest thing to do. File the thickened nail each time you trim your nails, or as needed.
Soak your nails for at least ten minutes in warm, soapy water.
Completely dry your toenails.
Use the emery board or file to reduce the thickness of the nail.
Keep the nail trimmed, starting at one corner and continuing straight across to the other corner. Smaller cuts with the trimmer will prevent splitting or chipping thick nails.
One important note: do not use cuticle pushers, which disturb the natural barrier that prevents the introduction of potential pathogens.
Prevention: A shoe with a larger toe box may help by giving the toes more room inside the shoe. Consult a physician if you suspect the problem is caused by an infection or other trauma.
Ingrown toenail: occurs when the edge of the nail irritates and eventually breaks the skin. Ingrown toenails are caused by several conditions, including genetics, trauma, infection, repetitive stress (usually in sports that require sudden stops), improper footwear, or improper trimming (too short or not straight across). The most common digit to become ingrown is the big toe, but ingrowth can occur on any nail.
Fix it: consider seeking immediate medical attention, or consult a nail specialist who will understand how to resolve the ingrown nail. In other words, treat yourself to a pedicure, or two.
A mild ingrown nail can be removed with careful clipping, but if it is deep or painful, consider a trip to the podiatrist. An unresolved ingrown toenail can lead to infection.
Prevention: proper cutting leaves the leading edge of the nail free of the flesh, precluding it from growing into the toe.
Never cut a V shape into the middle of your nail. Many people believe this technique is useful for preventing ingrown toenails, although it has been proven ineffective.
Footwear that is too small or too narrow, or a too shallow toe box, will exacerbate any underlying problem with a toenail.
Callus: areas of thickened skin caused by repetitive friction, or by abnormalities of the bony structure of the foot. Usually painless, calluses are a natural protective reaction of the skin over pressure sites.
Fix it: when a callus first develops, file it with an emery board or a pumice stone after bathing, and apply petroleum jelly, lanolin or other moisturizer to soften the area. Repeat this process as often as necessary. If a thicker callus has formed, you could use a peeling and softening agent such as Ultramide 25 lotion.
Runners may not want to totally remove calluses since they provide protection at pressure sites. However, if a callus becomes too big, it can crack, become tender, and it will be painful.
Calluses can also become tender on long runs or races from prolonged exposure to moisture from sweat. Blisters may also form under calluses. Resolve what is causing the callus, and it will go away on its own.
It’s good to regularly moisturize the feet (even for men). Consider products that contain tea tree oil since they are naturally antifungal.
Blisters: are small pockets of fluid under the skin caused by friction that can be a result of shoes that fit too tightly or too loosely. As your feet get wet with sweat the skin softens and leaves you at even greater risk.
Fix it: always leave a blister intact since an open blister can become infected. Cover the blister with an adhesive bandage/moleskin to protect it while it heals.
If it is particularly painful or uncomfortable, it may be necessary to drain the blister:
Wash your hands with warm water and antibacterial soap.
Using a cotton swab, disinfect a needle with rubbing alcohol.
Clean the blister with antiseptic.
Take the needle and make a small puncture in the blister.
Allow fluid to completely drain from the blister.
Apply antibacterial ointment or cream to the blister.
Cover the blister with a bandage, moleskin, or gauze.
Clean and reapply antibacterial ointment daily. Keep the blister covered until it heals.
You should visit a doctor if fever, nausea, or chills accompany a foot blister. This can be a sign of an infection.
Prevention: the most important step in preventing blisters is to identify the underlying cause.
If the blister is caused by friction, check your shoes to see if they are rubbing your foot in that area. Sometimes a seam or another design of the shoe can be the culprit.
If moisture seems to be the issue, apply foot powder to reduce sweating, (Dry Goods Athletic Spray Powder or Jack Black Dry Down Friction-Free Powder are two examples).
Wear moisture-wicking socks specifically designed for athletes. Socks with individual toes in the sock helps reduce friction between the toes that may cause blisters in some runners.
Over-striding can also cause blisters. This stride causes the foot to land in front of the body, absorbing the energy of the stride with a braking force that allows the foot to slide inside the shoe. Keep the stride short enough that the foot lands beneath the body rather than in front.
Bunions: a bunion is an (often unsightly) protuberance at the base of the big toe that forms when the metatarsophalangeal joint (MTP for short) is stressed over a prolonged period of time, causing the first metatarsal to turn outward and the big toe to point inward. (Bunions can also occur on the pinky toe.)
Fix it: the most important first step is to change your shoes.
High heels and pointy-toed shoes should be eliminated since they force the body’s weight forward, forcing the toes into the front of the shoe. Choose running shoes with a wide toe box, and consider shoes that have a lower heel drop (the height difference between the heel and forefoot often measured in millimeters).
Apply ice, use acetaminophen/ibuprofen, or visit your doctor for a cortisone injection for temporary pain relief. Using moleskin, gel-filled pads, or shoe inserts for arch support may also help.
Wear a toe spacer, starting with no more than 30 minutes a day. Two options are Correct Toes and Yoga Toes.
Try shoes that are wider at the end of the toes than at the ball of the foot and that do not have an elevated heel—what is known as “zero drop.” (This website has more info and specific shoe suggestions.)
Do a bunion massage – a bunion massage stretches the adductor hallucis.
Numbness or tingling sensation: numbness in the toes (unrelated to the cold weather) is often caused by shoes that are too tight or from tying your shoelaces too tight, but can also be caused by Morton’s Neuroma. This condition is caused when the tissue inside the foot becomes thicker next to a nerve that leads to a toe. The pressure against the nerve causes irritation and pain, usually between the third and fourth toes.
Morton’s Neuroma symptoms include:
tingling in the toes that may get stronger with time;
a burning sensation or numbness;
feeling like a pebble may be in your shoe, or that the sock is bunched up;
there may also be a shooting pain around the ball of the foot, or the base of the toes.
Choose shoes with a larger toe box.
Over-the-counter metatarsal pads can relieve the pressure, or your doctor may prescribe orthotics that are custom fit.
Some people find relief with cold therapy, which involves applying extremely cold temperatures to the irritated nerve to kill some of the nerve cells. There are also permanent surgical options, or a doctor may prescribe a corticosteroid shot.
Some runners have had success in resolving Morton’s Neuroma symptoms with a daily supplement of Vitamin B12.
Prevention: wearing high heels or shoes that are too tight can cause the tissues in the forefoot to thicken over time causing the neuroma. Be sure shoes fit correctly and that there’s plenty of room for the toes to move around inside the toe box. Women suffer from Morton’s Neuroma more often than men.
On a hot and humid summer day of 1904, thirty-two runners started a 24.85-mile course in St. Louis where water was provided at just two stations. The current thinking was that drinking during exercise was unnecessary. In fact, to compete without nourishment was a worthy achievement.
The high metabolic heat produced during exercise causes our core temperature to rise to dangerous levels (normal core or internal temperature is 98-100 degrees). The body’s counter measure is to increase the heart rate so that blood flow is maintained to the exercising muscles and the skin to allow for the dissipation of heat through sweating. When sweating becomes the primary means of heat dissipation, however, sweat loss must be matched by fluid consumption to avoid dehydration.
By 1923, the topic of exercise physiology was advanced by studies that emphasized the risks of dehydration during exercise. This research was the primary impetus for the “cardiovascular” model of physiology and thermoregulation, which predicts that there is a point at which increases in heart rate can no longer compensate, leading to reduced blood flow to the skin, an increase of core temperature, risk of heat stroke, or myocardial infarction (heart attack).
For decades, substantial research into hydration and performance supported the position that exercise performance is impaired when a level of dehydration due to sweating reaches about 2% body mass loss. The 1996 position stand of the American College of Sports Medicine (ACSM) stated, “Even a small amount of dehydration (1% body weight) can increase cardiovascular strain as indicated by a disproportionate elevation of heart rate during exercise, and limit the ability of the body to transfer heat from contracting muscles to the skin surface where heat can be dissipated to the environment.”
But these recommendations famously ignored evidence that some of the fastest marathon runners had incurred a water deficit exceeding 4%. Using data from a review of these marathon runners, when the relationship between running speed and percentage dehydration was plotted, the best-performing runner was dehydrated by some 8%, while the only runner to prevent body mass loss of >2% was the slowest (Fig. 1). The data suggests the effect of dehydration in excess of 2% did not impair performance significantly.
By 2007 ACSM’s revised consensus statement regarding fluid consumption during exercise reflected the new thinking that preventing all dehydration may be unnecessary, and that there may exist a level of “tolerable dehydration“.
New research has suggested that it is whole-body hyperthermia (defined as core body temperature exceeding 40°C; 104°F) that impairs performance rather than dehydration levels per se. In one study (Trangmar SJ, Chiesa ST, Kalsi KK, et al.), participants were placed under sufficient heat stress to either raise skin temperature or to raise skin temperature and core temperature. The participants with elevated skin temperature did not experience impaired exercise performance, whereas participants with an increase in whole body temperature did. This suggests a high sweat rate prevents a rise in core temperature (hyperthermia) even though it also results in a water deficit (dehydration). The higher sweat rate allowed the faster athletes to run faster than the slower runners because they were able to dissipate more core heat through sweating. We began to see that the best hydration strategy could only be determined by the athlete’s individual requirements rather than a one-size-fits-all recommendation.
The latestposition (2016) of the ACSM: ”Dehydration/hypohydration can increase the perception of effort and impair exercise performance; thus, appropriate fluid intake before, during, and after exercise is important for health and optimal performance. The goal of drinking during exercise is to address sweat losses which occur to assist thermoregulation. Individualized fluid plans should be developed to use the opportunities to drink during a workout or competitive event to replace as much of the sweat loss as is practical; neither drinking in excess of sweat rate nor allowing dehydration to reach problematic levels.”
Hydration theories have taken many turns. For example, we now know that a mixture of glucose, maltodextrin, fructose, sucrose and galactose – in other words, carbohydrates (also written as CHO), improves endurance performance by maintaining blood glucose and muscle glycogen stores, resulting in a levelling-off in core temperature. And so it was, with a mixture of sugar, salts and lemonade, the first sports drink was born.
The problem with these early sports drinks and gels is that our stomachs don’t always do well with high concentrations of sugar. Frequent GI distress prevailed over the next few decades of running.
A more recent innovation for providing fluid and CHO during exercise is the use of alginate. Alginate is a naturally occurring anionic polymer typically derived from seaweed and commonly used in oral drug delivery, wound healing, and tissue engineering.
Maurten is one such company delivering gels that are a combination of Alginate (extracted from the cell walls of brown algae) and Pectin (found in apples, lemons, carrots, tomatoes, etc.). When mixed with water, the resulting ‘sports drink’ converts to hydrogel in the acidity of the stomach, encapsulating the carbohydrates. Athletes that experience gastric (GI) distress from sugary sports drinks will appreciate that there were no reports of GI distress with any drink including the alginate hydrogel. And because it is engineered to encapsulate the carbs with the process beginning only when contact is made in the stomach, it is also better in terms of dental health.
Dental health is an important issue with CHO-based sports drinks. A survey at the London 2012 Olympic Games found that 18% of athletes reported that their oral health had a negative impact on their performance and 46.5% had not been to a dentist in the past year. (The latest ACSM position statement also addresses oral health in the wider culture of sports health care and health promotion.)
The next evolution in hydration began in 2014 when the Brazilian National Football Team asked Gatorade to help them prepare for the World Cup. The team didn’t end up winning the World Cup, but the pilot opened new doors for collaboration and innovation at Gatorade.
Smart Design worked with the Gatorade Sports Science Institute (GSSI) to research heat stress and dehydration during exercise. A systemized approach was developed to test and analyze how each athlete sweats—how fast, how much and in what concentration. The resulting product was a hydration platform – a bottle with a “smart cap” that’s built on the hypothesis that personalization is the next frontier of improving athletic performance.
Today’s consensus is that drinking to thirst is the body’s best hydration strategy, and in most cases will protect athletes from the hazards of over and under drinking by providing real-time feedback. It’s important to research and practice various hydration approaches during training runs to understand your specific needs, and to develop a personal strategy. Some athletes are less aware of their hydration requirements and may benefit from technology, such as a fluid calculator. But the quantity, amount, or combinations of food and/or fluid consumed while exercising should always be guided by your individual palatability and tolerance.
There is still a widespread misconception that you should ‘stay ahead’ of your thirst. Drink early and often was the advice we were given years ago; advice too many runners still follow.
Slower runners generally sweat less, but have been told to drink copiously. If you ingest more fluid than you lose through sweating or urination, however, you dilute your blood’s sodium levels – a condition called hyponatremia, or water intoxication, caused by drinking too much. Osmosis then draws water from the blood into body cells to equalize sodium levels, and those cells swell. If the cellular bloating occurs in the brain, it can be fatal.
The latest position statement from the International Marathon Medical Directors Association (2006) included a Final Word:
“There are no shortcuts toward great achievement, and marathon running is no exception. Clinicians and scientists must resist handing out unrealistic ‘‘blanket advice’’ to individuals seeking simple answers, but rather should encourage athletes to explore, understand and be flexible toward their own needs. By providing guidelines and advice on how to appropriately understand individual fluid replacement needs, we can eliminate future fluid balance problems by avoiding the temptation to generalize one rule for every situation and every athlete.”
My husband believes this more individualized protocol of hydration will serve to open up the sport to runners that may have otherwise found it too uncomfortable or difficult to participate. That in some way, having technology that explains how to hydrate will win them over to the sport. Maybe it’s even a marketing ploy on behalf of the corporations involved. I’m not sure I disagree.
To a seasoned runner, technological advancements may seem unnecessary. To a new runner, they may provide much needed guidance in a world of overwhelming challenges. It may or may not make you a better runner. Some would say technology is most useful at the far ends of the spectrum – in this case, for new runners and elite runners.
Many years ago I wore a special shoe with a piece of plastic in the bottom that could tell me how far I’d gone and at what pace. Some of you may have worn those same shoes. I suppose it helped me learn to pace myself better, but mostly it was new and fun.
When I ran in Kenya, a group of runners were heading out on a 40k training run. Knowing water was not easy to come by, I asked the runner I was with how often they would drink. He smiled and told me, “When they’re finished.” I used to never drink on a training run of any length. But there also came a time that I hid extra water bottles on my route and ate a peanut butter sandwich along the way. My main hydration strategy for race day was to try to avoid having to stop at the port-a-potty.
These new guidelines, and even more recent studies, emphasize that we are all unique and our hydration strategies will be equally unique. This left my husband feeling empty. He wanted something more absolute. I told him that now there’s an app for that.
A burglar is likely to experience flow, as is a con artist or an assassin. Flow is considered in the development of video games, sport psychology, computer programming, the design of playgrounds, the formation of business leaders, stand-up comedy, and in the high development training activities of Outdoor Leaders. Athletes, artists, musicians and Formula One drivers also experience flow.
Every activity in life may engender flow, but no activity can sustain it for long unless both the challenges and the skills become more complex.
flow: a level of involvement such that consciousness at hand and the doing of it blend; where action and awareness become indistinguishable.
In positive psychology, Flow, also known as Zone, is the mental state of operation in which a person performing an activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity…. complete absorption in what is doing.
Some runners report achieving flow, or in this case ‘the runner’s high,’ during a race or a tempo run – a run slightly below 10k race pace that is sufficiently taxing on the system but not an all-out effort.
Somewhere in this ideal zone runners lose themselves and reach a state where mind and body become one – the consciousness of running and the doing of it become indistinguishable.
According to Mihály Csikszentmihalyi (pronounced “CHICK-sent-me-high-ee”) who gave it the name, flow is completely focused motivation; a deep focus on nothing but the activity – not even oneself or one’s emotions. ”The ego falls away. Time flies. Every action, movement, and thought follows inevitably from the previous one, like playing jazz. Your whole being is involved, and you’re using your skills to the utmost.”
Csikszentmihalyi and his fellow researchers began researching flow after Csikszentmihalyi became fascinated by artists who would essentially get lost in their work. Artists, especially painters, become so immersed in their work that they disregard their need for food, water and even sleep.
He realized that it was the activity itself – the work of painting – that so enthralled his subjects and not, as he had expected, the anticipation of its outcome or extrinsic rewards. In Csikszentmihalyi’s initial 1975 studies, people described their experiences using the metaphor of a water current carrying them along – and thus his source for the name flow.
Research has shown that performers in a flow state have a heightened quality of performance. In a study performed with professional classical pianists, heart rate and blood pressure decreased and the major facial muscles relaxed while the pianists were in the flow state. This study emphasized that flow is a state of effortless attention. In spite of this effortlessness and overall relaxation of the body, the performance of the pianist improved during the flow state.
Drummers experience a state of flow when they sense a collective energy that drives the beat, something they refer to as getting into the groove or entrainment. Bass guitarists often describe a state of flow as being in the pocket. Surfers call it the surfer’s high.
Historical sources hint that Michelangelo may have painted the ceiling of the Vatican’s Sistine Chapel while in a flow state. Winning coach Jimmy Johnson credited flow with helping him and his Dallas Cowboys prepare for the 1993 Superbowl.
Each of these flow-producing activities requires an initial investment of attention and skills development before it can be enjoyable. If a person lacks the discipline to overcome this initial obstacle, he or she may find the state of flow impossible to achieve.
SOME CAN FLOW MORE THAN OTHERS….
Csíkszentmihályi hypothesized that people with specific personality traits may be able to achieve flow more often than the average person. These personality traits include curiosity, persistence, low self-centeredness, and a high rate of performing activities for intrinsic reasons only; known as an autotelic personality.
People with autotelic tendencies are internally driven and may also exhibit a sense of purpose and humility – this determination being different from an externally driven personality where things such as comfort, money, power, or fame are the motivating force. Autotelic personalities also learn to enjoy situations that other people consider miserable.
One researcher (Abuhamdeh, 2000) found that people with an autotelic personality have a greater preference for “high-action-opportunity, high-skills situations that stimulate them and encourage growth.” It is in such high-challenge, high-skills situations that people are most likely to enter the flow state.
THE PSYCHOLOGY. Almost any activity can produce flow, provided you find the challenge in what you are doing and then focus on doing it as best you can. Flow is not dependent on external events, but is the result of our ability to focus.
In every given moment, there is a great deal of information made available to our brain. Psychologists have found that one’s mind can attend to only a certain amount of information at a time – about 126 bits of information per second (Csikszentmihalyi’s 1956 study). Decoding speech, for example, takes about 40 bits of information per second; about 1/3 of our total capacity.
For the most part (except for innate basic bodily feelings like hunger and pain), we decide what we want to focus our attention on. When we are in the flow state, however, we are completely engrossed with the task at hand – without making the conscious decision to do so.
Awareness of all other things: time, people, distractions, and even basic bodily needs is non-existent. This occurs because our total attention is on the task at hand; there is no more attention to be allocated.
THE SCIENCE. The internet lit up in 2015 when German researchers discovered the brain’s endocannabinoid system — the same one affected by marijuana’s Δ9-tetrahydrocannabinol (THC) — may also play a role in producing the runner’s high, (Proc. Natl. Acad. Sci. USA 2015, DOI: 10.1072/pnas.1514996112).
For decades, it was hypothesized that exercise-induced endorphin release was solely responsible for a runner’s high. These researchers observed, however, that endorphins can’t pass through the blood-brain barrier. On the other hand, a lipid-soluble endocannabinoid called anandamide—also found at high levels in people’s blood after running—can travel from the blood into the brain, where it can trigger a high. Scientists agree more studies are needed since these conclusions were based on mice not humans, but it brings us a step closer to understanding the science behind the high.
HOW TO GET THERE. To achieve and maintain a flow experience, a balance is reached between the challenge of the activity and the runner’s ability.
If the challenge is greater than the ability, the activity becomes overwhelming and creates anxiety. Anxiety also occurs when the challenge exceeds our perceived skill level.
If the challenge is lower than ability, boredom ensues.
Apathy is characterized when the challenge is low, and one’s skill level is low – producing a general lack of interest.
A state of flow occurs when the challenge matches skill.
A 1997 study by Csíkszentmihályi also determined that flow is more likely to occur when the activity at hand is a higher-than-average challenge and the individual has above-average skills.
Defined within the parameters of a runner’s high, one could then assume flow would not be achieved when:
pace is too slow and effortless as compared to the runner’s skill level (boredom);
the runner has no interest in running (apathy);
pace or terrain, level of difficulty is too challenging (anxiety).
Knowing what to do
Knowing how to do it
Knowing how well you are doing (immediate feedback)
High perceived challenges
High perceived skills
Freedom from distractions
It’s important to repeat that the key to achieving flow is in one’s ability to focus.
A violinist will focus all their energy on feeling the strings or the bow with the fingers, following the notes on the score, and at the same time feel the emotional content of the music as a whole. Irrelevant thoughts, worries, or distractions no longer have a chance to appear in consciousness. There is no room. They are totally immersed and focused on the task at hand.
Similarly runners will feel a focus on running: the fluidity of the stride and the rhythm of breathing, the immediate feedback of feeling confident and comfortable in the effort – an exhilaration from performing a challenging task.
Some runners experience flow early in a run, near a 10k pace, or several hours into a long run, depending on their experience and skill level.
If there is a way to induce flow, it is by training the mind to focus. Techniques of meditation or yoga traditions train the ability to concentrate attention and limit awareness to specific goals and may be helpful in creating the conditions for flow.
THE GROWTH PRINCIPLE. Flow experiences imply a growth principle. When in a flow state, we are working to master the activity at hand. To maintain and achieve a subsequent flow state, however, we must eventually seek increasingly greater challenges. Attempting these new, difficult challenges stretches our skills and we emerge stronger, more competent, and with a greater sense of personal satisfaction.
Mihaly Csikszentmihalyi wrote a book on the subject, “Good Business: Leadership, Flow, and the Making of Meaning,” where he argues that with increased experiences of flow, people experience growth towards complexity, in which people flourish as their achievements grow.
In the long run, flow experiences in a specific activity may lead to higher performance in that activity as flow is positively correlated with a higher motivation to perform and to perform well.
This post reviews generic muscle characteristics and how they relate to runners, including muscle contractions, muscle/tendon/ligament injuries and treatment, muscle cramps and remedies, lactate, strength vs mass, slow vs fast, muscle fuel, endurance and loss, flexibility vs inflexibility, stretching and fatigue.
In a future post, we’ll look at how specific training methodologies affect each of these areas for short-, medium- and long-distance runners.
Key points from this post:
Muscle is a result of three factors that overlap: physiological strength (muscle size and responses to training), neurological strength (how strong or weak the brain’s signal telling the muscle to contract), and mechanical strength (the muscle’s force, leverage, joint capabilities).
The most common muscle injuries occur during eccentric loading and usually involve muscles that cross two joints, although the hip abductor muscles are also commonly affected even though they only cross the hip joint.
A stretched tendon can cause muscle spasms, but will typically resolve on its own. Ligament injuries can destabilize the associated joint and require many months, and sometimes surgery, to heal.
Eccentric training, such as downhill running, is the most effective in strengthening muscle and connective tissues, is effective for increasing flexibility, and can increase hip and joint range-of-motion, but is also known for causing muscle soreness (DOMS). Muscle rapidly adapts to the damage caused by eccentric training, however, and protects from the future damage of long distances.
Although the brain is responsible for creating strength (i.e., muscle recruitment), increased size or muscle mass (muscle hypertrophy) happens within the muscle. Following a period of inactivity, it is initially the brain’s ability to excite the muscle that declines in correlation with the muscle’s decrease in strength, rather than a physiological change in muscle size.
Our diets provide three sources of fuel: carbs, fat and protein. The body always uses a combination of carbohydrates and fat for fuel depending on the intensity of exercise. Low intensities use more fat, but by the time you’re gasping for air the proportions have flipped to mostly carbs.
Carb-free diets have become a popular way of encouraging fat burning, but there are trade-offs with this approach.
Lactate is an important source of energy, and is produced in muscles even at rest. The use of lactate as fuel varies with how well a person’s endurance muscle fibers are trained aerobically. Highly trained athletes use lactate more efficiently, which prevents it from accumulating to high levels in the muscle.
Protein is used as an energy source if calories are insufficient, although with sufficient calories, protein contributes only minimally to the total amount of energy used by working muscles.
In addition to strengthening teeth and bone, calcium also helps with muscle contraction. If a person’s diet provides too little calcium or too much phosphorus, their body siphons calcium out of teeth and bones and stops providing it to the muscles.
Exercise-induced muscle cramps have long been misunderstood to be caused by ”dehydration” and “electrolyte depletion” (water-salt imbalance). Muscle injury or muscle damage, resulting from fatiguing exercise causes a reflex ‘‘spasm’’, resulting in a sustained involuntary contraction, or cramp. Stretching is the most effective way to resolve cramps.
We break down and rebuild 1 to 2 percent of our muscle each day, meaning that you completely rebuild yourself every two to three months. The research shows you literally are what you just ate.
Studies show adults ages 50 and up with low muscle strength were more than twice as likely to die in follow-up periods of studies than those with normal muscle strength. Having low muscle mass (vs strength) didn’t seem to matter as much. The best outcomes of all were those adults who met the aerobic and strength-training guidelines: at least 150 minutes of moderate exercise or 75 minutes of vigorous exercise per week and performing a “strength-promoting exercise” at least twice a week.
When running frequency increases past 4 days a week or the intensity of endurance exercise increases above 80% VO2max, endurance exercise prevents the increase in muscle mass and strength typically associated with strength training.
Being inflexible creates greater elastic energy in the stretch shortening cycle. In fact, as much as 40-50% of the energy needed for distance running can be obtained from the elastic ability of skeletal muscle. Being less flexible is not as valuable for sprinters.
Static stretches before running caused a decrease in running distance, increased ground contact time during a 1-mile uphill run, increased muscle activation, and resulted in an approximately 8% decrease in performance.
In women, the variables related with muscle mass are generally 60-75% of the exercise physiology values recorded in men. When measured in terms of strength per square centimeter, however, the female muscle can achieve the same force of contraction as that of a male.
There are THREE TYPES OF MUSCLE in the body: 1) Smooth, involuntary muscles, 2) Cardiac heart muscle, and 3) Skeletal, or voluntary muscles that move the body, arms and legs. This post will focus on Skeletal muscle.
Muscle is a result of THREE FACTORS THAT OVERLAP: physiological strength (muscle size and responses to training), neurological strength (how strong or weak the brain’s signal telling the muscle to contract), and mechanical strength (the muscle’s force, leverage, joint capabilities).
Muscle tissue has THREE CHARACTERISTICS THAT GOVERN EXERCISE:
Contractility – Ability to shorten
Extensibility – Ability to stretch without damage
Elasticity – Ability to return to original shape after extension
The fundamental behavior of skeletal muscle is shortening, which produces joint motion and allows the body to move. Skeletal muscles attach to bones via tendons and often appear in antagonistic pairs, so that when one muscle contracts, the other lengthens.
THREE TYPES OF MUSCLE CONTRACTIONS:
Concentric contractions: muscle shortens, or contracts, pulling on the bone causing the joint to move. A reciprocal muscle on the other side of the joint contracts and shortens to return the joint to its original position. Muscles don’t push joints, they only shorten and pull.
Eccentric contractions: muscle shortens and lengthens at the same time, resulting in a resisting force to decelerate the lengthening movement. By opposing the downward force, a joint is safely repositioned and tissue is protected. Examples of eccentric contractions include walking down stairs, running downhill, lowering weights, and the downward motion of squats, push ups or pull ups.
Note: Eccentric training is effective for increasing flexibility, can increase hip and joint range-of-motion, and has been used as a form of training for several pathological conditions such as Parkinson disease (Dibble et al. 2006), and older cancer survivors (LaStayo et al. 2010),
The last form of muscle contraction is an isometric contraction where the muscle is activated but is held at a constant length rather than lengthened or shortened – there is no movement.
WHY IT HURTS
Muscle injuries commonly occur during eccentric loading of the muscle; that is, when the muscle is contracting while it is also elongating. Muscles that cross two joints, such as the hamstrings (the hip and knee joints), the calf (the knee and ankle joints), and the quadriceps (the hip and knee joints) are the most susceptible to injury. The hip abductor muscles are also commonly affected, though they only cross the hip joint. (Click here to discover more information about specific muscle injuries in other anatomy of a runner posts.)
Although exercises that involve eccentric contractions are the most effective in strengthening muscle, they are also the cause of muscle soreness. All forms of vigorous exercise can become painful, but only eccentric exercise causes delayed onset muscles soreness (DOMS). Muscles are very adaptable to eccentric exercises, however, and rapidly adapt to the damage, resulting in less muscle stiffness or soreness during a second bout of eccentric exercise.
When muscle is initially injured, significant inflammation and swelling occurs. Following the inflammatory phase, muscle begins to heal by regenerating muscle fibers from stem cells that live around the area of injury. However, a significant amount of scar tissue also forms where the muscle was injured. Over time, this scar tissue remodels, but the muscle never fully regenerates. This is thought to make injured muscle more prone to subsequent injury. Other factors that can predispose an athlete to injury include older age, less flexibility, lack of strength in the muscle, and fatigue.
Muscle (and tendon) injuries can be categorized into three grades ranging from mild damage to individual muscle fibers (less than 5%), causing minimal loss of strength and motion, to a complete rupture of the muscle or tendon.
Treatment and Recovery
The majority of acute muscle injuries are partial thickness tears. These can usually be treated successfully with rest, ice, compression, elevation (also known as RICE), and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen. This will be done for the first week, followed by progressive functional physical therapy, as needed. A return to full activity is usually possible when you are pain free, and when full range of motion and full strength is restored.
Recovery can be 2-3 weeks for Grade 1 injuries, or 2-3 months for Grade 2. The most severe injuries may require surgery to reattach damaged muscle and tendon. The resulting scar tissue of each injury makes athletes more susceptible to subsequent injuries at the same location.
In a study that examined professional football players with severe hamstring tears with palpable defects, an intramuscular cortisone injection led to a return to full activity time of 7.6 days, and 85% of the players did not miss a single game. However, the use of cortisone injections in the recreational athlete should be reserved for chronic or lingering injuries since there is a chance of weakening the remaining muscle and increasing the severity of the injury.
Several new therapies are in the investigational phase, including platelet-rich plasma (or PRP) which requires blood to be drawn and then spun in a centrifuge to concentrate the platelets and injected into the site of the injury. These platelets contain several growth factors that may stimulate healing and muscle regeneration, and limit the amount of scar tissue that forms. There are currently no reliable scientific studies that show if this therapy works. Antihypertensive medications have been shown to reduce scar tissue formation and improve healing in experimental models.
Tendon & Ligament Injuries
Tendons connect muscle to bone and ligaments connect bones to other bones. Tendons allow muscles to move bones, whereas ligaments stabilize joints. When tendons and ligaments are stretched beyond their basic capacity, they become damaged. For tendons, this can result in tendonitis, which occurs when the tendon becomes torn. This damage causes the tissue of the tendon to inflame while it heals; as a result, tendonitis causes swelling and soreness, as well as temporary loss of muscle function. Ligament injuries weaken the joint and threaten its integrity. A common ligament injury among athletes involves the ACL, or the anterior cruciate ligament in a person’s knee.
A stretched tendon can cause muscle spasms, but will typically resolve on its own. Ligament injuries can destabilize the associated joint and require many months, and sometimes surgery, to heal.
Tendonitis is inflammation of the tendon (the suffix “itis” indicates inflammation). Achilles tendonitis tends to be an acute (or quick-onset) condition lasting 6 weeks or less, although some view this diagnosis as the first in a continuum of tendon injuries that subsequently increase in severity.
Tendinosis is a non-inflammatory degeneration of the tendon which typically occurs from long-term overuse of the tendon leading to weakening of the tendon fibers. Unlike tendonitis, which can often be successfully treated within several weeks, tendinosis can take several months to treat.
Paratenonitis is inflammation of the tissue surrounding the tendon, which may thicken and adhere to the tendon. This diagnosis is controversial, as some practitioners do not believe paratenonitis is a separate condition from tendonitis.
Tendinopathy: The suffix “pathy” is derived from Greek and indicates a disease or disorder, in this case of a tendon. The term is also applied to a chronic condition that fails to heal. For example, a runner who has suffered a hamstring tendon rupture that does not heal properly may be diagnosed with tendinopathy.
SLOW VS FAST
Every muscle contains some combination of three basic types of fibers or motor units: slow twitch, intermediate, and fast twitch.
Slow-twitch fibers (Type I or Red Muscle) – are smaller, develop force slowly, maintain contractions longer, and have higher aerobic capacity that is well suited to long-distance/marathon oriented running. Red fibers are easier to target with exercise. For example, any repetitive, weight-bearing action above your accustomed-level intensity produces red muscle adaptations such as growth and increased endurance.
Fast-twitch fibers (Type IIx or White Muscle) – are larger, capable of developing greater forces, contract faster and have greater anaerobic capacity – better for sprinting or <400m races). White muscle specializes in high-intensity actions lasting fewer than 30 seconds and responds well to heavy resistance training and ballistic exercise such as fast, yet controlled, weightlifting, or plyometric training.
Intermediate fibers (Type IIa) – intermediate in size, speed, power, and susceptibility to fatigue such as those needed for prolonged fast running; the kind demanded for 800m and 1500m races.
Not all runners inherently have the same percentage of each type of muscle fiber. Elite distance runners have high percentages of slow-twitch and intermediate fibers, and as expected, sprinters have more fast-twitch. Since genetics determine our individual percentages, you may find you are more successful in sports that complement your specific muscle configuration. Finding your muscle type can be as simple as defining your preferences: Do you prefer long interval and tempo training (slow-twitch) or short, fast workouts (fast-twitch)? Despite genetic disposition, it has been suggested that training can cause type II fibers to take on the properties of slow-twitch type I fibers. (Specific training considerations will be covered in a future post.)
Muscles are recruited by the brain according to the Size Principle. Muscles with fewer slow-twitch muscle fibers are recruited first and, as more force is demanded by an activity, progressively larger, fast-twitch units are recruited. As the intensity of exercise increases in any muscle, the contribution of fast fibers also increases.
Top athletes in explosive sports like Olympic weightlifting or the high jump appear to have the ability to recruit nearly all of their motor units in a simultaneous or synchronous fashion. In contrast, the firing pattern of endurance athletes becomes more asynchronous. During continuous muscle contractions, some units are firing while others recover.
Initially we might maintain the desired pace/duration with no involvement from fast motor units. As these slow units become fatigued, however, the brain will recruit more motor units in an attempt to maintain pace. Recruiting these additional motor units brings in the fast, but easily fatiguable units. This explains why fatigue is accelerated at the end of a long or intense run.
Lactate is an important source of energy, and is produced in muscles even at rest – something that has been previously misunderstood. Lactate is sent to the brain and heart for fuel, or to active and inactive muscles for energy.
During exercise, we breathe faster to supply more oxygen to working muscles which also clears excess lactate. If exercise intensity increases beyond our ability to supply required oxygen, the muscles continue energy production, but in an anaerobic condition (without oxygen). The muscles produce energy in this anaerobic condition for only one to three minutes, during which time lactate can accumulate to high levels.
The potential for lactate accumulation varies by muscle type with fast-twitch muscles having the highest potential because of their maximum oxygen delivery requirements. “Producer” cells make lactate which is used by “consumer” cells. In muscle tissue, for example, the white, or “fast twitch,” muscle cells convert glycogen and glucose into lactate and excrete it as fuel for neighboring red, or “slow twitch,” muscle cells. Type II muscle fibers are highly glycolytic (they use lots of glucose) which results in the production of high amounts of lactate.
We’ve always associated these high levels of lactate with the burning sensation of muscle fatigue that ultimately causes us to stop exercise – a process that is thought to prevent muscle damage – although lactate may not actually be the cause of the burn. (Continuing research indicates muscle fatigue may be caused by other factors.) Lactate production is a strain response; it’s there to compensate for the metabolic stress of high intensity exercise. The deep breaths we take post-exercise helps clear excess lactate from muscles and restores balance.
The use of lactate as fuel within the muscle varies with how well a person’s endurance muscle fibers are trained aerobically. Highly trained athletes use lactate more efficiently as energy preventing it from accumulating to high levels. Conditioning in sports is all about getting the body to produce a larger mitochondrial reticulum in cells to use the lactate and thus perform better.
The muscles of untrained athletes, and also bodybuilders, produce energy without oxygen; a condition that produces high lactate levels in the muscles. At the same time, muscles begin to fatigue and the muscles feel “heavy”. This is considered an anaerobic training process (without oxygen) as compared to marathon training, for example, which is an aerobic (with oxygen) process.
Endurance training changes the metabolism of muscles by stimulating the production of a protein, PGC-1a. Trained mice that developed a high PGC-1a maintained their performance levels, and their lactate levels remained low despite a high training load. Endurance training programs, such as for the marathon, reduces the formation of lactate, while the remaining lactate in the muscle is converted and used immediately as energy substrate.
The energy drink, Cytomax, is based on research that indicates lactate is the body’s primary fuel. The combination of lactate, glucose, and fructose takes advantage of the different ways the body uses fuel: lactate can get into the blood twice as fast as glucose – peaking in just 15 compared to 30 minutes after drinking. Most sports drinks contain only glucose and fructose. (This reference is not an endorsement of the Cytomax product.)
1) High lactate levels are also seen in the blood during illness or after injury, such as severe head trauma, and are a key part of the body’s repair process. Lactate is now being used to help control blood sugar after injury, to treat inflammation and swelling, for resuscitation in pancreatitis, hepatitis and dengue infection, to fuel the heart after myocardial infarction and to manage sepsis.
2) Disturbances in lactate metabolism are common in obese and diabetic patients. The stimulation of PGC-1α achieved by endurance exercise means endurance training can be an effective approach to improve the metabolism of these groups, and could help prevent the resulting damage and progressive physical limitations caused by metabolic diseases.
POST EXERCISE OXYGEN DEBT
After exercise has stopped, extra oxygen is required to metabolize lactic acid and to replace (“pay back”) any oxygen that has been borrowed from other parts of the body. This debt is paid by labored breathing that continues after exercise has stopped. Highly trained athletes are capable of greater muscular activity without increasing their lactic acid production and have lower oxygen debts, which is why they do not become short of breath as readily as untrained individuals. Eventually, muscle glycogen must also be restored. Restoration of muscle glycogen is accomplished through diet and may take several days, depending on the intensity of exercise.
EXERCISE INDUCED MUSCLE CRAMPS (EAMC)
There are two theories about the origin of EAMC. The older one is the “dehydration” and “electrolyte depletion” theory (water-salt balance), while the more recent one is the “altered neuromuscular control” theory, or a sustained, involuntary muscle contraction brought on by muscle fatigue. In 1904, muscle spasms (cramps) were reported for the first time in two men at the Episcopal Hospital and were presented as a new disorder due to exposure to intense heat, which gave us the term “heat cramps”. Except, we’ve since learned that EAMC occurs in hot conditions, moderate to cool temperatures and in extreme cold. Also, multiple studies of endurance athletes, marathoners and triathletes have shown no evidence of low salt levels or electrolyte imbalances after cramping during a race (Schwellnus et al, 2004; Sulzer et al, 2005; Schwellnus et al, 2007).
One of the first studies showing that fatiguing muscle can develop cramping in normal healthy subjects during exercise was reported in 1957, but it wasn’t until 1997 that muscle fatigue was credited as the predecessor to EAMC. Click here to read the technical details behind this theory (Part III of a 5-part series on the history of EAMC studies) or here to read the full study.
A previous history of EAMC and a positive family history of cramping are also considered risk factors for EAMC. Muscle injury or muscle damage, resulting from fatiguing exercise, are thought to cause a reflex ‘‘spasm’’, and thereby result in a sustained involuntary contraction, or cramp.
Prevention & Recovery
Prevention of EAMC primarily is use of dietary supplements and kinesio taping, massage therapy, corrective exercises that will lead to the improvement of the function of a particular group of muscles or the biomechanics of the organism itself, although stretching exercises are said to be the most effective. Post-isometric relaxation techniques, plyometric or eccentric muscle strengthening programs have also proven effective. Mustard and pickle juice are listed as the nutritional form of EAMC prevention.
Note: non-exercise related cramps include rest cramps (also known as nocturnal cramps). These may be more prevalent in older adults, but can occur at any age. Rest cramps are started by making a development that abbreviates the muscle; for example, pointing the toe downward while lying in bed, which shortens/abbreviates the calf muscle, resulting in cramping of the muscle. Rest cramps can also occur in other areas, such as the arches of the feet or abdominal muscles.
STRENGTH VS MASS
Strength: People generate more strength if they can recruit and fire 50,000 muscle fibers than if they can only recruit 25,000 fibers. Muscle recruitment is controlled by the brain, and initial improvements are achieved because the brain gets more efficient at communicating with the muscles, using more of them, and using them more efficiently. In fact, muscle recruitment is the mechanism that allows us to gain strength before our muscles even increase in size. It is only through practice, or training, that the brain improves muscle recruitment.
Mass: Although the brain is responsible for creating strength (i.e., muscle recruitment), increased size or muscle mass (muscle hypertrophy) happens within the muscle. Microscopic damage (microtears) occurs in the muscle fiber during strengthening activities, which stimulates the body’s repair response to repair the damage. This repair response causes the muscle fibres to enlarge or swell, ultimately increasing their volume and size. Once running frequency increases past 4 days a week or the intensity of endurance exercise increases above 80% VO2max, however, endurance exercise prevents the increase in muscle mass and strength that typically occurs with strength training.
Note: Even with the greater muscle mass typically found in short distance runners, a sprinter cannot win a marathon. A sprinter’s specially-trained and strengthened muscles will fatigue faster than the endurance-trained muscles of a long distance runner. The research group of Prof. Christoph Handschin of the Biozentrum, University of Basel, shows that during endurance exercise the protein PGC-1α shifts the metabolic profile in the muscle.
The three basic fuel options are carbohydrate, fat and protein.
Fat is the preferred fuel for light-intensity to moderate-intensity exercise, such as slow running or hiking, cycling, and recreational swimming. However, the body always uses a combination of carbohydrates and fat depending on the intensity of exercise. Low intensities use more fat, but by the time you’re gasping for air, the proportions have flipped to mostly carbs.
Endurance (low-intensity) training teaches the body to preserve glucose and utilize more fat as fuel, but you’ll burn the same fat-carb mix at any given relative intensity. One study found that marathoners running a 2:45 pace relied on 97 percent carbohydrate fuel, while slowing to a 3:45 pace reduced the carb mix to 68 percent.
It is now believed that lactate is produced in healthy, well-oxygenated muscle and is preferentially used for energy throughout the body. In fact, about 30 percent of all glucose we use during exercise is derived from lactate “recycling” to glucose.
Carbohydrate-free diets have become popular in recent years to encourage the body to burn predominantly fat as fuel. Studies show it takes several weeks for the body to adjust to a mostly carb-free diet and that any benefits in terms of performance are mixed. In exchange for their enhanced ability to burn fat, a study of cyclists seemed to lose their ability to harness quick-burning carbohydrate for short sprints resulting in “a severe restriction on the ability of subjects to do anaerobic work.”
The conclusion among researchers is that high-fat (carb-free) diets don’t just ramp up fat burning; they actually throttle carbohydrate usage by decreasing the activity of a key enzyme called pyruvate dehydrogenase. This may or may not matter depending on your running goals. Fat burning is ideal for long distances that never require speed. Racing, on the other hand, may be enhanced by having carbohydrates in reserve for that end spurt, or for more intensive training sessions.
Protein is used as an energy source if calories are insufficient, although with sufficient calories, protein contributes only minimally to the total amount of energy used by working muscles. When a person begins a moderate endurance exercise program, they initially lose more protein than they ingest. This corrects itself within 2–3 weeks without dietary intervention. To increase muscle size and increase strength, however, athletes must ingest more protein than is lost. On the other hand, ingesting too much protein can result in dehydration, loss of urinary calcium, and will put stress on the kidneys and liver.
Luc van Loon, Professor at Maastricht University in the Netherlands, and his colleagues developed a technique to track protein as it progressed from a person’s mouth to their biceps in the hours following a meal. Just over 50 percent of the protein made it into the subjects’ circulation within five hours (the remaining protein was presumably taken up by tissues in the gut or not absorbed.) During the same period, 11 percent of the ingested protein was incorporated into new muscle. Literally, you are what you just ate. Overall, van Loon points out, we break down and rebuild 1 to 2 percent of our muscle each day, meaning that you completely rebuild yourself every two to three months.
Calcium is predominantly used by the body to strengthen teeth and bones, but also helps with muscle contraction. If a person’s diet provides too little calcium or too much phosphorus, their body siphons calcium out of teeth and bones and stops providing it to the muscles. Cola based soft drinks and some junk foods are high in phosphorous, unduly increasing the body’s need for calcium.
Fun Fact: studies in the 1960s found that people who retained more of their own teeth tended to have more muscle.
Our ability to engage in physical activity for long periods of time is thanks to efficient energy production in the mitochondria—the small “powerhouses” of our muscles. Endurance training increases the number of mitochondria and their structure, and the more we have, the longer we can exert ourselves. Endurance athletes have more than twice as many mitochondria that generate about 25% more energy as non-athletes.
During a two-week period following inactivity, it is the brain’s ability to excite the muscle that declines in correlation with the muscle’s decrease in strength, rather than a physiological change in muscle size. Getting older is another factor that causes changes within the muscle since muscles are less sensitive to protein signaling as we age. Studies show adults ages 50 and up with low muscle strength were more than twice as likely to die in follow-up periods of studies than those with normal muscle strength. Having low muscle mass (vs strength) didn’t seem to matter as much.
A similar study of 80,000 adults found those doing any strength training were 23% less likely to die and 31% less likely to die of cancer. The best outcomes of all – a 29% reduction in mortality risk – were those adults who met the aerobic and strength-training guidelines (at least 150 minutes of moderate exercise or 75 minutes of vigorous exercise per week and performing a “strength-promoting exercise” at least twice a week).
Note: A recent study led by researchers at Keele University has shown for the first time that periods of skeletal muscle growth are ‘remembered’ by the genes in the muscle, helping them to grow larger later in life.
Long-term observations of runners have shown improvements in running economy when the athletes are less flexible – being inflexible creates greater elastic energy in the stretch shortening cycle. In fact, as much as 40-50% of the energy needed for distance running can be obtained from the elastic ability of skeletal muscle. One of the reasons plyometric and resistance training improves running economy is due to an increase in muscle stiffness. Imagine a ball bouncing off a wall – if it gets softer, it bounces off more slowly, whereas a stiff ball returns quickly (golf ball vs squash ball, for example).
Being less flexible does not appear to be as advantageous in shorter distances, sprinting, or the long jump. A sprinter (i.e., events <800 m), for example, requires a greater range of motion at the hip that benefits from more flexibility as compared with a long-distance runner (i.e., events >800 m).
The sit and reach test is a common measure of flexibility, and specifically measures the flexibility of the lower back and hamstring muscles.
Researchers have sought to determine whether acute bouts of static stretching before exercise would affect running economy. (Static stretches hold a stretched or elongated position for 15 seconds or more.) Findings show runners who performed these stretches before running caused a decrease in running distance, increased ground contact time during a 1-mile uphill run, increased muscle activation, and resulted in an approximately 8% decrease in performance.
Stretching, considered an exercise, also fatigued the muscle resulting in more muscular recruitment to perform a given task. Considering that one of the adaptations to endurance training is asynchronous recruitment of the musculature, having to recruit more muscle fibers per given intensity would be counterproductive to performance for distance running.
Static stretching is helpful to increase range of motion or improve flexibility and is a useful component of an overall training program depending on your sport (i.e., for sprinters and short distance runners). If you feel a need to stretch before running, dynamic stretches use controlled movements that can make muscles more limber while also activating major muscle groups.
Fatigue was defined in a previous post as peripheral (within the muscles) or central (within the brain and spinal cord). Although fatigue produces the belief that our resources are limited, exercise generally ceases before all the muscle fibers have been activated. In fact, just 35-50% of active muscle mass is recruited during prolonged exercise. Read more here.
Limited studies show that women appear to be more resistant to fatigue than men during long efforts. A study that was published in the journal Medicine and Science in Sports and Exercise measured fatiguability of subjects completing an isometric arm contraction. Women were able to perform the task until failure almost three times longer than men, 23.5 minutes versus 8.5.
One difference between the sexes is that women have a greater number of fatigue-resistant fibers (Type I) while men have more faster-contracting fibers. Secondly, men have larger muscles that demand more blood, which makes their hearts work harder. Female endurance athletes also have a metabolic edge in moderate-intensity aerobic exercise by deriving more of their energy from fat as compared with males. In women, the variables related with muscle mass are generally 60-75% of the exercise physiology values recorded in men. When measured in terms of strength per square centimeter, however, the female muscle can achieve the same force of contraction as that of a male.
Note: Muscle fatigue is usually resolved within hours, while muscle damage can impair force generation for up to 7 days.
THE TRAINING EFFECT
Skeletal muscle has three basic performance parameters that describe its function: 1) Movement production (speed), 2) Force production (strength), and 3) Endurance. Increasing muscular strength will increase muscular power, which is the product of force (strength) and speed.
Athletic performance is ultimately limited by the amount of force and power that can be produced and sustained. The theories behind the various components of a running training program will be discussed in the next anatomy of a runner post.
American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Keele University. “Study proves ‘muscle memory’ exists at a DNA level.” ScienceDaily. ScienceDaily, 30 January 2018.
The topic of the next anatomy of a runner post is muscle. It’s not that we haven’t covered various muscles in previous posts, but their generic characteristics are fascinating as it relates to running and seem to warrant a separate conversation. After all, the brain and muscle are the most malleable of all the anatomical components. In other words, they can be trained.
The purpose of the paper is to illustrate the link between an athlete’s physiology and success in distance running. “The maximal oxygen (O2) uptake, O2 cost of running at sub-maximal speeds (running economy), and blood lactate response to exercise can all be determined using standard physiology laboratory exercise tests and the results used to track changes in ‘fitness’ and to make recommendations for future training,” Jones writes in the introduction.
Once or twice a year Radcliffe was given a physiological assessment that measured height, body mass, body composition (through skinfold thicknesses), haemoglobin concentration ([Hb]), pulmonary function, vertical jump height, a sit-and-reach test, and a multi-stage incremental treadmill test. The resulting data from these tests demonstrate how 15 years of directed training created the ‘complete’ female distance runner and a World champion.
Radcliffe committed herself to many years of hard training and used these yearly assessments to objectively analyze her progress and to inform her training. The data also accurately predicted actual finishing race times within 0.2-0.4% over a variety of distances.
Training consisted of “steady” continuous running, tempo runs, 1-2 higher intensity sessions at 95-100% V’02 max, interval or repetition sessions at the track or cross-country, and two weight training sessions weekly. Total mileage increased considerably over her career from less than 25-30 miles initially to 120-160 miles per week during full marathon training in the final years.
It’s difficult to pinpoint one thing that specifically creates an exceptional athlete although running economy, or enhanced exercise economy, is considered by many to be a critical component of success. Running economy is defined as the oxygen (O2) cost of running at a certain speed, or the O2 cost of running a certain distance. The more efficient we become the less oxygen we use, which means we can run further or faster with the same effort.
Radcliffe’s data demonstrate a 15% improvement in running economy between 1992 and 2003 suggesting that improvements in this parameter are very important in allowing a distance runner to continue to improve their performance over the longer-term.
There is evidence that explosive strength training can improve running economy. Studies of runners that participated in strength training decreased their running pace by 4% as compared to runners who did no strengthening exercises even though there were no significant changes in their maximum aerobic capacity, blood lactate accumulation, body mass, or body fat percentage. This is an important finding because it suggests that the improvements in running economy come from a mechanism other than cardiovascular or metabolic changes. A possible explanation is enhanced mechanical efficiency and muscle recruitment patterns – both of which are a result of the neuromuscular adaptations achieved from strength training.
As Radcliffe’s weight training program became more sophisticated her leg strength and power improved. Her vertical jump test performance improved from 29 cm in 1996 to 38 cm in 2003 while lower body “flexibility” declined slightly. This corresponds to a suggestion that “stiffer” muscle-tendon structures might improve running economy by allowing a greater storage and return of elastic energy (something we’ll pursue further in the upcoming post).
Exercise economy is influenced by a wide variety of factors so it’s not easy to say this or that is directly responsible for the improved running economy experienced by Radcliffe over her career.
One suggested explanation offered by Jones is that our type I (slow-twitch) muscle fibres are more efficient than type II (fast-twitch) muscle fibres; that is, compared to type II fibres, type I fibres consume less O2 for a given amount of muscle work, and if endurance training causes a reduction in type II fibres being recruited, this would reduce the cost of O2 and, therefore, improve running economy. Alternative studies also suggest that, with chronic endurance training, type II fibres take on some of the same properties of type I fibres, or that this same training results in a transformation of type II fibres into type I fibres.
You might ask, do we care? Depending on your running goals, the answer would be yes since the type and quantity of training causes a definitive change to the muscle structure and can affect performance across the spectrum of distances.
The distinction is made in this paper that while a high V ̇O2 max is a prerequisite for success at the highest levels of elite runners, and Paula Radcliffe certainly had this, factors such as running economy and a delayed accumulation of lactate in the blood are also important and can be positively affected by our training.
Mr. Jones concluded the paper by saying,
“Study of the great human athletes therefore continues to provide insights into the ultimate limits to exercise performance. Through determination, commitment, and consistently hard training, PR has achieved her athletic potential and become one of the greatest endurance athletes of all time. I have been greatly honoured to have been associated with her.”
The upcoming post about muscle will include a behind-the-scenes kind of look at the types of training that create the most improvements for runners, strength vs mass, slow vs fast, elastic energy or active stretch, fatigue and endurance.
THE BRAIN is what makes us human. It gives us the capacity to make decisions, produce rational thoughts, or spectacular works of art. It’s responsible for our personality, storing the memories we cherish, and how we view the world. It also governs our ability to speak, eat, breathe, and move.
Disciplined, smart training is the foundation of any athletic endeavor, and proper training is also what earns us a seat at the table of endurance. Some athletes have genetic endowments and natural advantages that predispose them to sports. Maybe they respond better to training, the shape of their bodies or the genes they carry make them specifically optimized for certain athletic endeavors. Another subset of great athletes also have cultural and environmental advantages, such as the Kenyans who spend a lifetime being active at altitude. Then there are great athletes who have none of these advantages – the only common denominator between all groups of athletes being the brain.
The question of this post is not what can the human body do, but rather, what more can the human mind add to that?
The 1922 Nobel Prize in Physiology or Medicine winner, Archibald Hill, proposed in 1924 that the heart was protected from anoxia (absence of oxygen resulting in permanent damage) in strenuous exercise by the existence of a governor. Dr. Timothy Noakes, a professor of exercise and sports science at the University of Cape Town, re-introduced Hill’s governor model in 1997 on the basis of modern research. The essence of Noakes’ original central governor theory is that the brain monitors activity, predicting outcomes, and involuntarily implements an appropriate pace that prevents total exhaustion and permanent bodily damage by creating the distressing sensations we interpret as fatigue.
Physiological catastrophes can and do occur in athletes, however, that present conflicts in the governor theory. A story from the 2015 Austin Marathon serves as one example from many.
Kenyan runner, Hyvon Ngetich, had been leading most of the race. With two-tenths of a mile left to run, she began to wobble and stagger, and eventually fell down. After failed attempts to get up, Ngetich crawled to the finish line leaving her knees and elbows bloodied and hands stained from the pavement. Ngetich crossed the finish line in third place with a time of 3:04:02, and was immediately treated for dangerously low blood sugar. In a post-race interview with CNN, she said she didn’t remember finishing the race. She had continued the race despite the distressing sensations of fatigue and debilitating physiological failure.
Over time the central governor theory has been revised to include the role of psychological and motivational factors, which is where we begin to uncover the story of endurance.
muscular endurance: the ability of a muscle or group of muscles to repeatedly develop or maintain force without fatiguing.
cardiorespiratory endurance: the ability of the cardiovascular and respiratory systems to deliver blood and oxygen to working muscles, which in turn enables the working muscles to perform continuous exercise. It is an indicator of a person’s aerobic or cardiovascular fitness.
athletic endurance is defined as the ability to continue an activity despite increasing physical or psychological stress, as in the effort to perform additional numbers of muscle contractions before the onset of fatigue.
The human brain weighs about 3 pounds (1.4 kilograms). The surface area is 233-465 square inches (1500-2000 cm2), or roughly the size of one to two pages of newspaper. If we flattened the brain’s 1/4 inch thick outer layer, it would cover the size of an office desk. But to keep the brain compact enough to fit into our skull, it folds in on itself.
The simplest commands of the brain are monosynaptic (single connection), like the knee-jerk reflex. The knee-jerk response is a muscular jerk that happens quickly and does not involve the brain. There are lots of these hardwired reflexes, but as tasks become more complex, the circuitry involved is more complicated, and the brain gets involved.
The cerebellum, “little brain”, consists of both grey and white matter, and is responsible for coordinating muscle movement and controlling balance by transmitting information to the spinal cord and other parts of the brain. The cerebellum is constantly receiving updates about the body’s position and movement. It also sends instructions to our muscles that adjust our posture and keeps our body moving smoothly.
The cerebrum is the largest part of the human brain, controlling memory, movement, speech, emotions, and voluntary motor activities. With the assistance of the cerebellum, the cerebrum controls all voluntary actions in the body. Voluntary actions include running, clapping your hands, or lifting weights – things you are consciously doing.
The cerebral cortex is the outer layer of the cerebrum and consists of gray matter. This is where our conscious thoughts and actions take place; many of the signals our brain receives from our senses are registered in the cerebral cortex.
Basic life functions, such as heart rate, breathing, and blood pressure, is carried out by the brain stem. It regulates whether we feel tired or awake, as well as coughing, sneezing, and swallowing. The brain stem is the body’s “autopilot”.
About the size of a pearl at the base of the brain, the hypothalamus regulates physiological processes, such as blood pressure, heart rate, body temperature, cardiovascular system function, fluid balance, and electrolyte balance. This portion of the brain plays a vital role in maintaining homeostasis: the process of maintaining the body’s equilibrium by monitoring and adjusting physiological processes. It also influences emotional responses, sleep, appetite, and tells the skin to produce sweat when it’s hot to keep you cool.
The hippocampus (HC) region of the brain deals with the formation of long-term memories and spatial navigation. In diseases such as Alzheimer’s, the hippocampus is one of the first regions of the brain to become damaged, which leads to memory loss and disorientation.
The atrophy rate of the hippocampus (HC) is shown to be 2-3% per decade (Raz et al., 2004, 2005), and further accelerated to an annual loss of 1% over the age of 70 (Jack et al., 1998). Recent research, however, has shown the HC is among a few regions of the brain that generate new neurons.
In particular, exercise causes hippocampal neurons to pump out a protein called brain-derived neurotrophic factor (BDNF), which promotes the growth of new neurons. Higher cardiorespiratory fitness levels (VO2 max) are associated with larger hippocampal volumes in late adulthood, and larger hippocampal volumes may, in turn, contribute to better memory function (Erickson et al., 2011; Szabo et al., 2011; Bugg et al., 2012; Maass et al., 2015). (22)
Running Fact:A study published in the Journal of Neurobiology of Learning and Memory finds that running mitigates the negative impacts chronic stress has on the hippocampus region of the brain. “Exercise is a simple and cost-effective way to eliminate the negative impacts on memory of chronic stress,” according to the study’s senior author, Jeff Edwards, associate professor of physiology and developmental biology at BYU.
THE PERSONALITY OF A RUNNER
Observational studies have identified common personality traits among runners, including a strong vision, focus and resilience. Runners consistently exhibit mental toughness, an extraordinary capacity to plan ahead, and the ability to handle unexpected problems with a calm yet competitive demeanor; we are more willing to accept feedback, and acknowledge our mistakes.
Imaging of a runner’s brain show connections in areas required for higher-level thought, including more connectivity between parts of the brain that aid in working memory, multi-tasking, attention, decision-making, and the processing of visual and sensory information. Less activity is noted in a part of the runner’s brain that tends to indicate lack of focus and mind wandering. (24)
A 2009 study found ultra-marathoners were less dependent on rewards (self-motivated), they were more individualistic, and, not surprisingly, exhibited a far greater tolerance for pain. Studies of older runners show them to be more intelligent than their non-running peers, more imaginative, self-sufficient, reserved, and forthright.
The most common trait among runners of all ages is the belief that they possess the resources needed to achieve their own success. (13) (14)
Running Fact: An abstract presented at the 2018 American College of Sports Medicine Conference indicate runners who exhibit ”perfectionist” tendencies were 17 times more likely to suffer an injury that forced them to miss training as compared to other runners.
When we exercise, the brain recognizes this as a moment of stress, and invokes a “fight or flight” response. The body’s protection mechanism to this new threat is to release the BDNF protein in the brain. The greater the exercise intensity, the more BDNF proteins are released. At the same time, endorphins, another stress-reducing chemical, is released in the brain. The main purpose of the endorphins is to minimize discomfort and block the feeling of pain, sometimes also associated with a feeling of euphoria.
As exercise continues, physiological changes are signaled to the brain, such as body and skin temperature, increased heart and breathing rates. These signals are interpreted by the brain and compared with previous experience to determine allocation of resources.
The brain begins to change as soon as the athlete begins a sport, and the changes continue for years. In just one week, athletes develop extra gray matter, and different regions of the brain begin to interact – some neurons strengthen their connections to other neurons as they weaken their connections to others.
After deciding on a specific goal, to run a fast lap around the track for example, several regions of the brain collaborate to determine the best course of action to complete that goal. Initially, neurons in the front of the brain (the prefrontal cortex) are active; a region vital for the top-down control that enables us to focus on a task and consider a range of responses. By predicting what sensations should come back from the body if it achieves the goal, the brain can match the actual sensations received and revise its plan if needed to reduce error. With practice, however, the prefrontal cortex grows quiet; our predictions get faster, more accurate, and the brain becomes more efficient, learning to make decisions sooner.
In just a few sessions of exercise we become stronger, but not because our muscles have suddenly increased in size. The initial gains that take place are neuromuscular adaptations: the brain gets better at communicating with the muscles, using more of them, and using them more efficiently. The brain also learns to tolerate heat, lack of oxygen, and muscle pain. It becomes better at suffering. In essence, the brain is changing.
Neuroplasticity, or brain plasticity, is the process in which your brain’s pathways are altered as an effect of environmental, behavioral, and neural changes. Neuroplasticity occurs as the brain deletes connections that are no longer necessary or useful while strengthening the necessary ones. Which connections are pruned and which are strengthened depends on life experiences and how recently connections have been used. Neurons that grow weak from underuse die off while new experiences and learning new things strengthens others. In general, neuroplasticity is a way for your brain to fine-tune itself for efficiency. To learn new tasks, you need good plasticity.
Neuroplasticity affects both short-term memory (chemical changes) and long-term memory (structural changes). Initial changes in the brain’s structure take place quickly, showing immediate results. These changes are imbedded in short-term memory, but to transfer these changes to long-term memory requires more time (practice). It takes time and repetition for the brain to re-wire new connections, or pathways, that create long-term learning.
Practice is not a new concept for athletes. Distance runners build mileage gradually to teach their bodies to endure long distances, and then we practice these runs until our body transfers the distance to long-term memory. Sir Roger Bannister learned to run the 4-minute mile in the same way. He reduced the race to its simplest common denominator – 400m in one minute or multiples thereof, and trained until running 400m in a minute, 24 km per hour, became automatic.
The third way the brain changes is in function – how and when neurons are activated. Although each of these changes can take place in isolation, chemical, structural and functional changes typically work in concert to facilitate learning.
Fun Fact:Neuroscientist Charles Limb and others have scanned rappers’ brains during a freestyle rap and during a memorized rap. The studies show that during freestyling, there’s a functional change in their neural networks. Through practice, the rappers have reorganized their brain activity, allowing their improvised lyrics to bypass many of the conscious-control portions of the brain, which regulate behavior.
The greatest discovery regarding neuroplasticity is that nothing affects the brain more than our own behavior, and nothing is more effective than practice to help you learn. In fact research shows that increased difficulty, or increased struggle during practice actually leads to more learning and greater structural change in the brain. These studies have also identified the best methods to prepare, or prime the brain to learn include brain stimulation, exercise, and robotics. (33)
The important take-away, something confirmed from cancer treatments and the study of stroke victims, is that the way our brain functions is unique to each person. It goes beyond the fact that we all learn differently. Every human brain processes commands, makes connections, and functions differently. So the common denominator in learning is practice.
Skill athletes (basketball players, dancers, gymnasts, figure skaters) show greater motor cortex plasticity while endurance athletes (cross-country skiers, orienteers, runners) show enhanced plasticity in task-unrelated brain areas.
Motor Cortex Plasticity In Action: Giannis Antetokounmpo’s slam dunk.
In a blatant show of coordination and focus, Antetokounmpo snared the ball mid-air with his right hand while soaring over the head of Knicks’ guard Tim Hardaway Jr. without seeming to notice the obstacle at all – and then slammed the dunk.
THE LIMITS OF HUMAN ENDURANCE
Fatigue refers to the inability to continue exercise at a given intensity. In all sports and exercise training, the onset of fatigue varies depending on a person’s fitness level, exercise intensity, duration, and environmental conditions (e.g., heat and humidity). Fatigue develops over time, but is largely dependent on duration and intensity.
There are two distinct types of fatigue: central and peripheral. Central fatigue (also called Central Nervous System fatigue) involves the brain and spinal cord rather than the muscles. Central fatigue happens in the regions of the brain involved with mood, emotion, and psychological arousal. This is why being psyched, such as during competition, can help performance, but is also why fatigue, like pain, is relative.
With central fatigue, the brain becomes unable to send enough signals to the muscles to maintain optimal muscle activation, resulting in general body fatigue (tiredness, loss of drive, sleepiness, etc.) and reduced muscle force.
Peripheral fatigue results from the muscles becoming fatigued. A lack of resources within the muscle results in the accumulation of lactic acid, causing a burning sensation and fatigue within the muscle. Although both central and peripheral fatigue result in decreased performance of the muscles, they follow different mechanisms.
The question is, how much can you separate the two? It’s hard to distinguish central fatigue (the brain) from peripheral fatigue (the rest of the body) because the brain tends to influence everything, and is in turn influenced by everything.
THE CENTRAL GOVERNOR
Although fatigue produces the belief that our resources are limited, exercise generally ceases before the muscles are depleted. In fact, in all forms of exercise fatigue develops before all skeletal muscles are recruited. Just 35-50% of the active muscle mass is recruited during prolonged exercise (Tucker et al., 2004; Amann et al., 2006), and even during maximal exercise this increases to only about 60% (Sloniger et al., 1997a,b; Albertus, 2008).
Muscle biopsies from cyclers revealed that intramuscular measurements were no different at exhaustion compared to rest, and that these (ATP) levels never dropped below 50% of resting concentrations at any time during the exercise bout, suggesting fatigue causes people to terminate exercise well before muscle energy reserves are depleted (Noakes & Gibson, 2004; Parkin, Carey, Zhao, & Febbraio, 1999).
This supports the updated theory that fatigue is a central (brain) perception – a sensation or emotion – and not a direct physical event. Exercise seems to be regulated in anticipation to insure biological failure never occurs (in healthy humans).
Based on studies done at the time, this new definition of fatigue supported the idea that a central governor reduces the mass of muscle recruited during prolonged exercise gradually to prevent the development of muscle glycogen depletion and muscle rigor, or of hyperthermia leading to heat stroke. In other words, fatigue is one way the brain protects the body and preserves homeostasis by regulating power output – what runners will recognize as pacing.
If fatigue is an emotion, it will (like pain) be perceived differently by different people. Ultimately, the Borg Scale of Perceived Exertion was developed, which matches how hard you feel you are working to a “relative” scale of numbers from 6 to 20. The physical sensation of fatigue increases along the Borg RPE scale as a linear function of exercise duration. Maintaining a strategy that follows this linear increase of effort has been thought to produce the optimum pacing strategy (start slow/easy, finish faster).
The Borg RPE scale has since been described as the manifestation of information about body temperature, oxygen levels, fuel storage, and the more subtle indicators like mood or how much you slept last night. Perceived effort (RPE) gradually increases based on a combination of these psychological and physiological changes. Runners probably don’t consciously correlate pacing to the Borg scale, however, and researchers disagree as to the extent pacing decisions/computations take place consciously and voluntarily or unconsciously and automatically. Where they do agree is on effort: how hard it feels dictates how long you can sustain.
Understanding how we control the feeling of effort is still being studied, especially as it relates to pacing. Two concurrent studies recently looked at pacing methodologies. One uses an effort-based approach where runners increased pace based on self-determined effort rather than the traditional approach of pre-set increments along an increasing scale (start slow/finish faster). The effort-based subjects reached higher VO2 max values. This study, by Alexis Mauger, was co-published in the British Journal of Sports Medicine alongside another study (by Noake’s student, Fernando Beltrami) which used a “reverse” protocol that started fast and gradually slowed. This protocol produced higher than “max” VO2 max values.
Alex Hutchinson aptly summed up these conclusions in his book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance, ”If you execute a perfectly paced race, that means you effectively decided within the first few strides how fast you would complete the full distance. There’s no opportunity to surprise yourself. . .”
Once exercise begins, pace is continuously modified by continuous feedback to the brain from conscious sources including information of the distance covered (Faulkner et al., 2011) and of the end-point (duration and intensity). Studies show an athlete’s perceived exertion can be positively influenced by knowing the duration of an exercise bout, and that energy is held in reserve and available for an end-spurt regardless of their rating of perceived exertion (RPE). (27) (28).
Other conscious deceptions that improve performance and positively impact RPE include sudden noise, music, seeing the finish line or an encouraging smile, rinsing the mouth with carbohydrate (without actually ingesting the fluid), being provided with inaccurate information by a clock that runs slowly, or the pace of a prior performance that had been deceptively increased by 2%, and a host of psychological factors, including hypnosis.
Interestingly, just swishing a glucose solution in the mouth led to improvements in 1-hour cycling performance, whereas intravenous infusion of glucose did not (Carter, Jeukendrup, & Jones, 2004.) These effects are probably not specific to glucose; recent evidence suggests that simply handling ibuprofen without ingesting it promotes pain relief, for example (Rutchick & Slepian, 2013). Glucose is absorbed almost entirely in the gut, so it would be impossible for glucose briefly swished in the mouth to cause an increase in available blood glucose (Gunning & Garber, 1978). Instead, the presence of glucose in the mouth may simply provide an anticipatory signal of glucose availability, which leads some experts to argue that the body’s glucose resource issue is one of allocation, not of limited supply. (32)
The Greatest Human Strength
RPE prevents the athlete from continuing exercise at a given pace when it might cause bodily harm. This anticipatory regulation, or pacing, balances the desire for optimal performance with the requirement to defend homeostasis. You may not even notice the body’s regulatory reaction at first, but gradually the effort required to sustain a given pace increases. Ultimately, exercise is terminated when the perceived effort reaches a level that is considered higher than the perceived benefit. (25) This conscious decision of whether to maintain, increase or decrease the current workload or indeed to terminate exercise altogether may be the outcome of a balance between motivation and the sense of effort.
One of the most obvious characteristics of human exercise performance is that athletes begin exercise at different intensities, or paces, depending on the expected duration of exercise – a bout of short duration is begun at a much faster pace than one of longer duration. Also, athletes typically run harder in competition than in training. The point is that athletes always show an anticipatory component to their exercise performance that seems to be influenced by neural mechanisms relating to willpower (self-control), motivation and belief.
In 2013, at 64 years old, Diana Nyad set out to be the first person to swim from Havana to Florida without a shark cage. A marathon swimmer can expect chafing, nausea, severe shivering and hypothermia, swollen lips, an irritated mouth, diarrhea, extreme weight loss, and sleep deprivation. At the peak of her strength, age 28, she tried but failed to complete this swim. She later said: “I never had to summon so much will power. I’ve never wanted anything so badly, and I’ve never tried so hard.” Coming back to the sport 30 years later, she claimed, “I thought I might even be better at 60 than I was at 30. You have a body that’s almost as strong, but you have a much better mind.”
Nearly 53 hours after jumping into the ocean in Havana, Nyad finished the 110-mile (180 km) swim; her fifth attempt since 1978 and the fourth since turning 60. In one interview she said, “ — you tell me what your dreams are. What are you chasing? It’s not impossible. Name it.”
Research has suggested that self-control relies on a limited resource – that it unfortunately appears to wane over time similar to a muscle that becomes fatigued with overuse. Humans are less willing to exert effort the longer they have already exerted effort. This so-called ‘ego depletion’ effect has been supported by over 200 separate studies, which show that repeatedly resisting temptation drains your ability to withstand future enticements. With the right motivation, however, it appears you may be able to persevere even when your willpower strength has been depleted.
Motivation combines internal and external factors to stimulate the desire and energy to be continually interested, committed to, or make an effort to attain a goal. It is the result of conscious and unconscious factors such as the (1) intensity of desire or need, (2) incentive or reward value of the goal, and (3) expectations of the individual and of his or her peers. These are the reasons we behave in a certain way. (35)
When motivational arousal is high and must be concentrated within a brief period, the intensity of motivation must also be great. It is the difference, for example, between moving 100 pounds of books one book at a time or all at once, or running an all-out 400m challenge versus enduring a 10,000m race or marathon. Motivation tends to increase as the difficulty of the task increases until the required effort is greater than is justified by the motive – or the required effort surpasses the individual’s skills and abilities. At this point motivational arousal drops. We can see this play out time and again on the marathon course where runners find the reward of finishing the race no longer surpasses the pain of continuing to run.
An increasingly accepted body of exercise physiology has emerged that looks to psychology to understand endurance. This ‘psychobiological model based on motivational intensity’ theory (Brehm and Self, 1989; Gendolla and Richter, 2010) suggests that perception of effort and potential motivation are the central determinants of exercise duration, with people consciously deciding how much or how little effort to apply based on a number of considerations. These new studies suggest endurance is strongly influenced by the manner in which the brains of runners generate the sensations of fatigue.
Remember that fatigue is an emotion entirely self-generated by each athlete’s brain, and therefore unique to each individual – or illusionary. Based on this model, the winning athlete is the one whose illusionary symptoms [of fatique] interfere the least with actual performance.
But psychologists have also found evidence among athletes in what they call “self-efficacy,” or a belief in their own competence and success. This is where self-efficacy converges with the placebo-effect.
Studies repeatedly confirm that interventions such as sugar pills, ice/cold/lukewarm baths, massage, caffeine, beet juice, altitude training, or even a “lucky” ball, in the case of golfers, improve our game. Athletes everywhere swear by them, yet science repeatedly proves the effects are null or ambiguous at best.
Christopher Beedie, a sports psychologist at the Canterbury Christ Church University in England, is among the few scientists who study the placebo effect in athletics. His work often examines how elite athletes perform under intense fatigue when they think they have some kind of performance enhancement.
Beedie recently finished the largest placebo study ever done in athletics—600 subjects in all—and found that the people most likely to respond to placebo were the ones experienced using supplements. Perhaps the previous supplements the athletes had taken primed them to have a placebo response, or maybe athletes who naturally respond to a sports placebo are also likely to have taken performance enhancers. Either way, it suggests that artificially boosted performance and performance boosted from expectation produce similar effects. In some cases, athletes performed better when given a sugar pill than the athletes that were given certain performance enhancing drugs.
Even in the arena of these performance enhancing drugs and placebos, especially for elite athletes, there’s a limit to the benefits of both psychological and pharmacological performance enhancers, so why not just use belief instead? “We’re trying to educate athletes into the idea that the headroom is there to be filled, and drugs are not necessarily the only way of filling that headroom,” Beedie says. “Confidence is the drug of champions.”
In the end, the question we all share is how do we go further/longer/faster; what is the secret of endurance?
Dr. Lara Boyd, Director of the Brain Behaviour Lab, is a physical therapist and a neuroscientist leading the effort to understand what therapies positively alter patterns of brain activity after a stroke. In a research-based TEDx Talk, Boyd describes how neuroplasticity gives you the power to shape the brain you want.
The new discovery is that learning changes our brains differently. My brain will go about learning a new task differently than your brain will learn the same new task. Understanding these differences, these individual patterns, is the future of neuroscience – and possibly sports science as well.
Boyd suggests we understand how we learn. What is it that your brain responds best to? For runners learning to endure, maybe this means experimenting with self-talk, visualization, or forcing yourself to try a new training approach altogether. Coaches are increasingly realizing they can push athletes to new limits just by asking them to do something they didn’t think they could do.
Even when athletes were sufficiently motivated, by monetary rewards or recognition for example, they did not perform as well as athletes who were led to believe they could accomplish the task.
Humans keep doing impossible things. Running a 4-minute mile, running 100 miles, lifting 500 pounds over our head, being an undefeated wrestler with no arms or legs. Each of these things have been accomplished even though public opinion claimed they were impossible at the time. The difference was that in each example these people believed, or were tricked into believing they could do this thing.
The pursuit of endurance is a unique journey for each of us, but it seems science has concluded what athletes have known all along – that there’s more in the tank, if you’re willing to believe it’s there.
A 2017 animal study published in the journal Behavioural Brain Research concluded that a sprint interval training regimen, rather than intensive endurance training regimen has the potential to improve anxiety and depression through a greater increase in (brain-derived neurotrophic factor) contents in the brain.” (10)
A NOTE ON MUSIC: Diversionary techniques to distract the mind, such as listening to music or self-talk, were discussed in a previous post on Pain, and have proven effective in lowering the perception of effort. Music, in particular, can narrow attention and divert the mind from the sensations of fatigue. However, this holds true for low and moderate exercise intensities only; at high intensities, perception of fatique overrides the impact of music. At high intensities, the physiological feedback to the brain regarding things like respiration rate or blood lactate accumulation dominates the conversation, and music fails to divert the mind from the body’s feedback. Listening to music seems to shape how the mind interprets symptoms of fatigue, however, which may enable athletes to perform more efficiently resulting in greater endurance. (16)
Studies demonstrate that running economy significantly changed, along with perceived effort, based on whether the runners knew they were running 20 minutes or whether they did not know the duration, even if they ended up running 20 minutes.
In a recent study published in BMC Medicine, the 64-day ultramarathon TransEurope FootRace Project followed 10 ultra-endurance runners covering about 4,500 km from Bari, Italy to the North Cape, Norway recording a large data collection of brain imaging scans. This study indicates cerebral atrophy among the runners amounted to a reduction of approximately 6% throughout the two months of the race, but was completely reversed within the 6-month follow-up. The results of this unique study, which revealed no brain lesions, gave clues to the effect of extreme fatigue with energy deficits on cortical grey matter volume. Having an understanding of what the brain does during an ultra-marathon event could help refine research on the matter of mind over muscle in determining exercise tolerance in endurance athletes, but may also benefit military personnel involved in physical work over prolonged periods and patients affected by unexplained chronic fatigue syndromes.
A 2011 study (Erickson et al.) demonstrated that 1 year of aerobic exercise increased the volume of the hippocampus by 2% in elderly adults, while controls who underwent 1 year of stretching exercises exhibited a 1.4% decrease in hippocampal volume.
Kids who participated in vigorous physical activity scored three points higher, on average, on their academic test, which consisted of math, science, English, and world studies. (23)
Telling runners they look relaxed makes them burn measurably less energy to sustain the same pace. Giving rugby players a post game debriefing focused on what they did right rather than what they did wrong had effects that continued to linger a full week later. (34)