Eating during exercise is a learned skill that requires considerable planning and testing and includes discovering tasty nutrient sources along with the amounts and timing that work best for you. This demands careful trial and error and meticulous attention to detail. Don’t assume that just because certain sources work well for someone else, they will also work well for you. Tolerance for food during exercise is an individual matter.
The workouts that are the best indicators of what you can or cannot eat are the ones that most closely simulate the event for which you are training, including the expected race duration, intensity, terrain, and weather. You will find that your body’s tolerances for food and fluid change as conditions vary. The least important priority C races on your schedule that mimic the conditions of the priority A events serve as even better tests for nutrition because these also place psychological demands on you. The ultimate test is the goal race. From this experience, you can draw even better conclusions for future races.
The intensity of exercise has a great deal to do with how well the stomach tolerates food and drink. At very high intensities, such as above 85 percent max VO2 (approximately at anaerobic threshold), the gastrointestinal system essentially stops functioning as blood is shunted to the hardworking muscles and to the skin for cooling. Conversely, at low intensities, such as when racing in an ultra-marathon event that takes many hours to complete, many athletes experience an as-yet-unexplained mechanism that produces nausea. Fortunately, if the event for which you are training is short and intense, such as a 5-K run or bicycle criterium, there is no need to take in additional fuel. You have plenty on board already.
If, on the other hand, your event is long and not a steady effort but, rather, punctuated by high-intensity efforts that determine the outcome, such as a bicycle road race, then eating and drinking must occur at times when the intensity is low. The nausea associated with very long events, such as Ironman triathlons or ultra-marathons, isn’t as simple. Among the possible reasons for the queasiness:
Poor pacing. This is the most common cause of nausea early in a long, steady race. Going too fast in the early stages—perhaps because of nervous energy and a poor pacing strategy while simultaneously taking in food, whether solid or liquid—causes the digestive tract to fill excessively. Due to the high intensity, the gut doesn’t process what’s taken in. Continuing to consume calories even after the intensity has settled at a more conservative level just exacerbates the problem. Slowing down dramatically and temporarily stopping food intake are the only solutions.
Excessive fluids. Another possible cause of nausea in long-duration events is overdrinking. The stomach can hold roughly 32 ounces and empties at a rate of approximately 30 to 42 ounces per hour, depending on body size and exercise intensity. If the stomach’s reservoir capacity is exceeded, as can be the case with poor race-nutrition planning and a lack of refueling rehearsal, it has no choice but to remove the excess by vomiting.
Excessive nutrients. Related to the last cause is another: taking in food or drink that is excessively concentrated with nutrients. The greater the fuel’s nutrient content, the slower the stomach processes it. While physiology textbooks say that, on average, the stomach empties about 6 calories per minute, or 360 calories per hour, most long-distance athletes know it is possible to handle far more than that—perhaps as much as 600 calories per hour (and maybe even more in some large athletes). There seems to be a lot of variation in individual tolerance for food volume. Whatever your limit, slightly exceeding it for several hours will eventually lead to the stomach overfilling, with but one solution—puking.
Dehydration. Excessive dehydration in the heat may also contribute to nausea. If fluid intake is well below one’s sweat rate for a long period of time, body fluids are shunted away from the digestive system to the skin (for cooling) and muscles (for work production). When that happens, the processing of fuel and fluids is reduced. In other words, the stomach’s emptying rate falls and whatever is taken in accumulates until the excess triggers nausea.
Saltwater ingestion. In ocean-swim events, such as Ironman-distance triathlons or long-distance swimming, swallowing seawater may set up the athlete for nausea later in the event. “Seawater poisoning” occurs when the high sodium content of ocean water causes the stomach to shut down until the gut’s sodium content is diluted, preferably by drinking plain water. If the athlete does not gradually take in water to dilute the sodium, or if he or she takes in fuel in any form (including liquid), the body will make its own adjustments by pulling water from the blood and intracellular space into the stomach or by vomiting.
None of the above. Your gut’s displeasure during a given event could be due to several of the above scenarios—or it could be caused by something altogether different, such as nervous excitement, food poisoning, exhaustion, or extreme heat. It may also be that your body, while in good shape, is not yet fully prepared for a long-distance event. An extreme event relative to your fitness level may simply overwhelm your body’s ability to cope.
The good news is that once you vomit, it’s likely that you’ll start feeling better. But don’t get carried away by the newfound relief—the problem could soon come back to haunt you. At this point, slow down if you haven’t already, and begin sipping water to see how that is accepted. If your stomach seems to handle that for 10 to 20 minutes or so, progress to a diluted drink by mixing water and a sports beverage. Take in only 2 to 3 ounces over 10 to 20 minutes. Again, if that stays down, try a normally concentrated sports drink. At some point, you will know that the conservative approach is working and you can resume a greater intensity, but be cautious; your stomach may still be upset. Even though this may cost you time, it is better to finish than to make the DNF (did not finish) list.
Athletes are generally greatly concerned by dehydration. After a poor race performance, especially on a hot day, they are likely to blame the less-than-stellar experience on excessive loss of body fluids. Recent research is showing, however, that the level of dehydration necessary to affect performance is greater than formerly believed. The trend is toward accepting dehydration at some level as a normal condition of exercise. For example, the American College of Sports Medicine in 1996 concluded that athletes should prevent any level of dehydration by continually replacing all water lost during exercise. By 2007 the ACSM’s position had changed due to concerns about excessive drinking resulting in hyponatremia (discussed later in this chapter), a far worse problem than dehydration. They now advise athletes to restrict water losses during exercise to less than 2 percent. But even that is questionable.
The clinical evidence is not overwhelming that losing 2 percent of body weight due to sweat is harmful to your health or to endurance performance. In fact, field studies conducted on athletes at long-distance races in hot and humid conditions, such as the Ironman Triathlon World Championship in Kailua-Kona, Hawaii, find that athletes continue to perform at very high levels with body-weight losses of 3 percent or even greater. Some exercise scientists point out that the most dehydrated athletes in a race are typically the first to finish. They certainly were not slowed down by body-weight losses of greater than 2 percent.
Body weight is not recommended as a way to determine your fluid needs. For, after all, while racing or training you don’t have the opportunity to weigh yourself to gauge fluid replacement needs. Nor can you use past experiences when you’ve weighed before and after exercise. There are many variable conditions when you are training and racing that impact fluid levels. Small changes in air temperature, humidity, wind speed, exercise intensity, exercise duration, altitude, hydration status at the start line, glycogen storage levels, and other factors affect how much fluid your body loses through sweat and breathing. Knowing that one set of such conditions caused a loss of a certain amount of body weight does not mean that all exercise will result in the same or even similar losses. So how should you gauge fluid losses to prevent what could be excessive dehydration?
The answer is simple: thirst. Somehow, athletes have come to believe that thirst is not a good predictor of their body’s fluid needs. It’s likely due to effective marketing by sports drink companies, which has been shown to have a great influence on what athletes believe about hydration. If thirst does not work for humans, then we would be the only species in the animal world to have such a condition. And it’s unlikely that as a species we would have flourished and spread around the world to so many extreme environments.
Early humans evolved while running and walking long distances in the heat of the dry African savannah while hunting and gathering. Water was not readily available. There were no aid stations. They drank just enough to maintain healthy fluid levels, but not necessarily body weight. The key to this delicate balance, now as much as 10,000 years ago, is the sensation of thirst. If you learn to pay attention to how thirsty you are and drink enough to satisfy it, you will no longer need to be concerned with body weight. Nor will you need a “drinking schedule,” which is, at best, based on flimsy conclusions about what the many conditions will be during exercise. It’s actually quite simple: If you are thirsty, drink; stop drinking when you are no longer thirsty.
Let’s address another rehydration issue common in endurance sport—the need for sodium intake to maintain or even improve performance.
During exercise, as fluid is lost through sweating and breathing, the concentration of sodium in the body actually increases. The reason is because much more fluid than sodium is lost through sweating. One might sweat off around a liter of water during intense exercise on a warm day, but lose only a tiny amount of sodium. Normal body sodium levels are about 140 millimoles per liter (mmol/l) of water while the level of sweat is about 20 to 60 mmol/l.
So let’s say an average-size human body contains 40 liters of water when at rest and normally hydrated. That means it has stored away something like 5,600 mmol of sodium (40 x 140 = 5,600). If 1 liter of fluid is lost during exercise and with that 60 mmol of sodium is excreted (the high end or “salty” sweater), then the new sodium concentration is about 142 mmol/l (5,600 - 60 = 5,540 / 39 = 142.05). The concentration of sodium has risen, not declined. Guess what happens next after a sufficiently large rise in sodium concentration occurs? Your thirst mechanism kicks in and you drink water to dilute the sodium, bringing it back down to something closer to 140 mmol/l. A study by Hubbard and associates found that a rise of about 2 or 3 percent of plasma sodium concentration evoked a strong desire to drink.
So your sodium content becomes more concentrated during exercise as you sweat, not less, as we’ve been led to believe. In other words, you don’t need to replace lost sodium during exercise because the loss is inconsequential, while the volume of water lost is significant. But even if you did, the sodium content of most sports drinks is only 10 to 25 mmol/l, not enough to replace the loss. More than that makes the drink unpalatable. The extracellular fluid in your body, where much of the sodium is stored, has about the concentration of seawater. If you’ve ever swallowed seawater, you know how nasty that would be as a sports drink.
Would not taking in sodium during a long race or workout impact your performance? Not according to the research. For example, a study by Merson and associates found that adding sodium to a sports drink did not improve performance in a time trial effort after 4 hours of exercise at a moderate intensity. Similarly, a study by Barr and associates found that sodium in a sports drink did not impact the ability to complete 6 hours of moderate-intensity exercise.
Should you take in sodium at all during a race or workout? There is no known downside to doing so. In fact, there may be a slight advantage, but not for the reasons we’ve been led to believe. A bit of sodium may improve the rate of absorption of both water and carbohydrate in the upper part of the small intestine. Sodium during exercise also is known to expand blood plasma volume, increasing the amount of blood pumped by the heart for each stroke. That’s a good thing. And after exercise, extra sodium may be needed to prevent dilution in the cells as water is taken in to recover from the slight dehydration that occurred. So the bottom line is that it’s okay to take in sodium during and after a race or workout.
The greater issue for the long-duration athlete is hyponatremia—low sodium concentrations in the body fluids. This can lead to not only poor performance but also acute health problems and even death. In recent years there have been two reported deaths in marathons related to over-hydration-induced hyponatremia. Both were back-of-the-pack runners who had been on the road for several hours. Studies of Ironman-distance triathletes have shown that many competitors experience mild levels of hyponatremia.
This condition is considered to be a sodium concentration level of less than 135 mmol/l by some experts. The most common way this occurs is through dilution of sodium stores caused by overdrinking during exercise. So the main issue is not replacing sodium, but rather not drinking too much fluid. Thirst is the key to this balance. If you drink only when thirsty and to a level that satisfies thirst, then you will not drink too much. Drinking as much as possible, which used to be a common tip for athletes, or drinking to a predetermined schedule during events lasting longer than about 4 hours, has the potential to cause hyponatremia.
Hyponatremia occurs when the sodium concentration of the blood is reduced to dangerous levels. It can result from prolonged vomiting or diarrhea or from taking diuretics; but in endurance athletics, it’s most commonly seen with excessive intake of fluid during long events. And the fluid doesn’t have to be water. The death of one of the two marathoners mentioned above occurred from overdrinking a commercial sports beverage. Even though these drinks have sodium as an ingredient, they do not maintain a healthy concentration if you drink to excess. Hyponatremia is extremely rare in events lasting less than 4 hours, but it’s common in competitions taking 8 or more hours to complete. In studies at the New Zealand and Hawaii Ironman Triathlons, events that take 8 to 17 hours to complete, researchers found that up to 30 percent of finishers experienced mild to severe hyponatremia.
How does this happen? In a mistaken belief that one cannot take in too much water during exercise, the athlete overhydrates and may even gain weight during the event. The problem is most common with slower participants because they have greater opportunity and more time to drink. (The fastest athletes are more prone to dehydration than to hyponatremia; they find it more difficult to take in fluids at their level of competitiveness, plus they spend less time on the course.)
It can be difficult to determine if you are experiencing hyponatremia because the signs come on slowly. Early symptoms include headache in the forehead, nausea, muscle cramps, lethargy, confusion, disorientation, reduced coordination, and tunnel vision. One sure sign of hyponatremia is bloating. Look for puffiness and tightness around rings, watches, sock bands, and elastic waistbands. In extreme cases, the athlete may experience convulsions, unconsciousness, respiratory distress, or cardiac arrest. Because urination is greatly reduced or stops altogether when blood sodium concentrations are low, hyponatremia is often misdiagnosed as dehydration—and that can be a fatal error. If water intake is increased in a mistaken attempt to rehydrate the athlete, the condition worsens.
Let’s now examine the unique nutritional characteristics of workouts and races of various duration ranges.
These are the shortest exercise sessions that qualify as endurance activities and include 800-meter through about half-marathon runs, sprint-distance triathlons, bicycle criteriums and time trials, some mountain bike races, 5-K to about 30-K cross-country ski races, and most rowing events.
What sets such events apart from longer-distance racing is the high intensity. At the pace the athlete is traveling, taking in solid food is out of the question and, thankfully, not necessary. The focus of nutrition during training or racing for these events, regardless of one’s speed, is on hydration, which is resolved by drinking enough to satisfy thirst.
Assuming adequate nutrition in the days and hours preceding a 2- to 90-minute session, the athlete’s body is well prepared with glycogen stores. The risk of bonking is quite low for experienced athletes. Novices and weekend warriors may need to assume their starting point for taking in carbohydrate is 60 minutes, because they don’t store as much glycogen in their muscles. There is no harm in novices or advanced athletes using a sports drink, regardless of the duration. Some research has even found performance benefits from the intake of a sugar-based fuel source in events lasting less than an hour. Interestingly, one study found that rinsing one’s mouth with a sports drink and spitting it out improved performance in relatively short events. The mechanism for this isn’t understood and the research is contradictory.
With this in mind, however, the greatest nutritional need at this duration is water. As explained above, it’s best to drink enough to satisfy your thirst. In such a short race, that may not be possible, especially for the fastest athletes, who find it difficult to move at high speed and drink at the same time. There should be little cause for concern if that is the case. With such a short event, dehydration is unlikely to be sufficient to harm your health or even to result in a poor performance.
Examples of race events in this range are half- to full-marathon runs, Olympic to half-Ironman-distance multisport races, bicycle criteriums and road races, mountain bike races, and 30-K to 100-K cross-country ski events. Longer workouts at a more leisurely effort are also included here.
At this duration, inadequate nutrition and environmental stresses on the body begin to take a toll on performance. All athletes are at risk for depleted muscle glycogen stores, and very fast athletes face the possibility of dehydration, so nutritional goals must begin with taking in adequate fluids and carbohydrate. It is best to use a sports drink or gel with water to maintain carbohydrate stores. Take in 200 to 300 calories per hour, depending on your body size and experience. The longer the event, the more important it is to replenish fuel stores.
From the outset of the exercise session, replace some of the expended glycogen to delay the onset of fatigue while maintaining power. Do not wait until the latter stages of the workout or race to take in carbohydrate, as that may well set you up for a poor performance or even a bonk. The carbohydrate at this duration is best in a liquid form. There is little reason to use solid foods. Assuming a good nutritional intake before the event and the consumption of carbohydrate throughout, food in solid form will have no marked advantage, but the potential for nausea at race intensity is significant.
Especially for longer events in this range, using sports drinks and gels instead of only water has the added advantage of limiting muscle damage. For high-intensity exercise sessions, the body will turn to protein for a fuel source as glycogen stores run low. Much of that protein will come from muscle. Failing to get adequate carbohydrate during intense exercise at the longer end of this duration range can result in muscle wasting.
In studies comparing the effects of carbohydrate and water on perceived exertion during intense exercise at this duration, carbohydrate was the clear winner. This means that even though your heart rate and blood acidosis levels may be the same whether you drink water or a sports drink, the effort will feel lower with the sports drink. The combination of carbohydrate and protein (primarily the branched-chain amino acids, described in Chapter 4) may enhance performance and postexercise recovery, while helping to prevent the transport of excessive amounts of serotonin to the brain. Serotonin is a chemical that can cause the onset of central nervous system fatigue, accompanied by increased sensations of exertion and even sleepiness. The research on sports drinks that combine carbohydrate and protein is not conclusive. When carb-only and carb-plus-protein drinks with equal amounts of calories are compared in such studies, there is generally no significant performance improvement. For some athletes, the consumption of protein during exercise seems to contribute to nausea.
For the shorter end of this duration range many athletes will get by with minimum fuel intake. When exercising at maximum intensity for the longer end of this duration, take in up to 200 to 300 calories per hour in an equal distribution every 10 to 20 minutes, primarily from liquid sources. The minimum intake is 1 calorie of carbohydrate per pound of body weight per hour.
As always, drink enough to satisfy your thirst. Doing this is a skill that must be developed in training and priority C races, as some athletes become so focused on performance that they forget to pay attention to their thirst. High glycemic index drinks with much greater maltodextrin or glucose than fructose content are preferred, as some athletes experience gastrointestinal distress from even a moderate amount of fructose. Most commercial drinks include at least some fructose. Let experience be your guide.
Consider using a caffeinated sports drink or gel; this has been shown to enhance the utilization of the glucose in sports drinks. The mechanism here is not fully understood, and research in this area is limited. Could using caffeine result in an upset stomach? In the only study on this topic, conducted at University Hospital, Maastricht, Netherlands, there was no difference in the stomach-acid levels of the people using drinks with caffeine and those who didn’t use caffeine. But as always, it’s best to experiment with caffeinated drinks in training and priority C races than to try them for the first time in an important event.
For the better part of a century, athletes and physiologists alike have considered lactic acid a primary cause of fatigue during high-intensity exercise and referred to it as a “waste product” of muscle metabolism. But now this way of thinking has changed, as scientists have learned that this substance we produce in large quantities during exercise, especially highly intense exercise, is not a cause of fatigue and actually helps to prevent it.
The former misrepresentation started with British physiologist and Nobel laureate Archibald V. Hill, who in 1929 flexed frog muscles to fatigue in his lab and noted that lactic acid accumulated when muscular failure occurred. He concluded that the lactic acid caused the fatigue associated with repeated muscle contractions. What he didn’t know is that when the muscle is examined as part of a complete biological system instead of in isolation from the rest of the body, we can see that lactic acid is processed and converted to fuel to help keep the muscles going. It does not cause fatigue.
Nor does lactic acid cause muscle soreness the day after hard exercise. This myth has been around for decades and refuses to go away, despite evidence to the contrary over the past 30 years. Soreness is more likely the result of damaged muscle cells resulting from excessive usage.
So if lactic acid is not the villain we’ve made it out to be, what does cause fatigue and the burning sensation in the muscles during short, intense exercise bouts, such as intervals or races lasting just a few minutes? To get at the answer, it’s necessary to understand the pH scale, which tells us how acidic or alkaline (base) the body’s fluids are in a range of 1 to 14, as hydrogen ions increase or decrease. On this scale, hydrogen readings dropping below neutral 7 indicate increasing acidity, while those rising above 7 indicate escalating alkalinity. Examples of acidic fluids are hydrochloric acid (pH = 1) and vinegar (pH = 3), while milk of magnesia (pH = 10.5) and ammonia (pH = 11.7) are alkaline.
At rest, the pH of your blood is around 7.4—slightly alkaline. In terms of your blood, small absolute changes in acid-base balance have major consequences. For example, during a 2- to 3-minute all-out effort, your blood’s pH may drop as low as 6.8 to 7.0. In biochemical terms, this is a huge acidic swing, producing a burning sensation in the working muscles and an inability for them to continue contracting. Fatigue has set in.
If lactic acid didn’t cause the drop in pH, what did? The answer has to do with our sources of fuel during such short exercise bouts—glycogen and glucose. Both are carbohydrates, but they have slightly different chemical compositions. Glycogen is stored inside the muscle, where it can be quickly broken down to produce energy. Glucose, a form of this carbohydrate-based fuel that is stored in the liver and floats around in the bloodstream, is called on to produce energy for exercise when muscle glycogen stores can no longer keep up with the demand or are running low. As glycogen is broken down to produce energy, it releases one unit of hydrogen. But if glucose must be used for fuel, such as when the intensity of the exercise exceeds glycogen’s ability to keep up, two units of hydrogen are released. This rapid doubling of hydrogen ions in the system lowers the blood’s pH, causing the burning and fatigue associated with acidosis. The same amount of lactic acid is released no matter which fuel is used.
Far from being an evildoer, lactic acid is an ally during intense exercise. It does a great deal to keep the body going when the going gets hard. Besides being converted back into a fuel source, when hydrogen begins to accumulate, lactate transports it out of the working muscle cells and helps to buffer or offset its negative consequences.
After 80 years, lactic acid’s bad boy reputation has been lifted.
At this duration we are moving into events in which the athlete’s health and well-being during exercise cannot be taken for granted. Hyponatremia, as described earlier, is now a real threat, and nutritional planning is critical in ways other than simply performance.
Races in this range include marathon and ultra-marathon running, half-Ironman- to Ironman-distance events, bicycle road races and century rides, and ultra-marathon cross-country ski and rowing events.
At such durations the intensity of exercise is quite low, with the effort seldom, if ever, approaching the anaerobic threshold in most sports. The exception is bicycle road racing, in which episodes lasting about 2 minutes during breakaways occur at a highly anaerobic level. With this exception, the fuel source for long, steady events is now very heavily weighted in favor of fat, with carbohydrate playing a smaller, but no less important, role. There is an old saying in exercise science that “fat burns in a carbohydrate fire.” In the real world of endurance athletics, this means that if carbohydrate stored as muscle glycogen runs low, the body will gradually lose its capacity to produce energy from fat. In other words, a bonk is highly likely during events in this category if carbohydrate ingestion is neglected for even a little while. Once an athlete is well behind the carbohydrate intake versus expenditure curve, catching up is difficult and may be accomplished only by slowing dramatically or stopping exercise altogether. This is the dreaded “death march” so commonly found late in these events.
Carbohydrate must be taken in right from the beginning of these sessions in order to stay close to the expenditure rate, delaying the onset of fatigue while maintaining power. Although replacing most of the expended glycogen is the goal for this duration, it’s doubtful you will be able to restock all of it. At the highest intensities, the fastest athletes expend about 1,000 calories per hour, with perhaps up to 60 percent of that coming from carbohydrate-based glycogen. It’s unlikely that all but the largest athletes consume that much carbohydrate. In fact, you don’t need to replace it at all if you did a good job of eating quality carbohydrate in the 24 hours leading up to the race or workout. If you did, you have probably stored 1,500 to 2,000 calories as carbohydrate in your muscles and liver, depending on your body size. By keeping the hourly deficit (exercise expenditure minus intake) at less than 100 calories, even the elite athletes in the longest of these events—those who are likely to burn the most calories—can avoid bonking. Slower athletes can keep the deficit even smaller, but that isn’t particularly a problem because their burn rate is lower.
In such events, get about 200 to 400 calories per hour in an equal distribution every 10 to 20 minutes, primarily from liquid sources with a minimum of 1 calorie of carbohydrate per pound of body weight per hour. At the upper end of this race-duration range, around 12 hours, sports bars or even solid foods may be used as desired. Solid foods must be of moderate to high glycemic index, low in fiber, and easily digested.
Some athletes have success when using commercial meal-replacement drinks at durations of about 8 hours or more. If you decide to experiment with these, it’s best to avoid those that use dairy products as the primary source. Unfortunately, most drinks in this category are largely cow’s milk. One exception is Ensure.
Otherwise, the guidelines for carbohydrate fuel replacement are the same as in the previous section, including the possible use of a caffeinated drink with added protein. As with the 90-minute to 4-hour events, taking in some protein may help prevent the onset of central nervous system fatigue, which is marked by general malaise and even yawning—even though you’re consuming adequate carbohydrate and aren’t particularly bored. But once again you must consider the possible downside of nausea. Experiment in training and low-priority events to see if the addition of protein to your sports drink can be managed by your gut.
The elite athlete’s greatest concern at this distance is dehydration. Slower athletes should be able to easily avoid this calamity by drinking when thirsty, but they need to be aware of overdrinking resulting in hyponatremia, as described above. Overhydrating with water by as little as 2 percent can bring on this dreaded condition.
Solid food is more likely to be needed only during the longest events in this range, although some athletes continue to use only liquid sources of fuel even when approaching 12 hours.
We’ve all had it happen. The race is going great—then all of a sudden, from out of nowhere, a muscle begins to feel “twitchy” and seizes up. You slow down, hoping it will go away. It does, but as soon as you start pouring on the power, it comes back. The promise of a stellar race is gone.
There is no more perplexing problem for athletes than cramps. Muscles seem to knot up at the worst possible times—seldom in training, but frequently in races.
The real problem is that no one knows what causes cramps. There are theories, the most popular being that muscle cramps result from dehydration or electrolyte imbalances. These arguments seem to make sense—at least on the surface. Cramps are most common in the heat of summer, when low body-fluid levels and decreases in body salts due to sweating are likely to occur.
But the research doesn’t always support these explanations. For example, in the mid-1980s, 82 male runners were tested before and after a marathon for certain blood parameters considered to be likely causes of muscle cramps. Fifteen of the runners experienced cramps after 18 miles. There was no difference, either before or after the race, in blood levels of sodium, potassium, bicarbonate, hemoglobin, or hematocrit. There was also no difference in blood volume between the crampers and the noncrampers, nor were there significant differences in the way the two groups trained.
Note that we are talking about exercise-induced cramps here. In such cases of cramping, the knotted muscle is almost always one that is involved in movement in the sport. If depletion of electrolytes was a cause of cramping during exercise, why wouldn’t the entire body cramp up? Why just the working muscles? Electrolytes are lost throughout the body, not just in working muscles. We know that people who become clinically hyponatremic by losing a great deal of body salts (not exercise-induced) cramp in all of their muscles. It’s generalized, not localized.
It should also be pointed out that when someone cramps, the “fix” is not hurriedly drinking a solution of electrolytes, but rather stretching the offending muscle. For example, a runner with a calf cramp will stop and stretch the calf muscle by leaning against a wall or other object while dorsiflexing the ankle against resistance—the standard “runners stretch.”
In fact, what is known is that sweat, with regard to electrolytes, is hypotonic. That means the concentration of sodium, potassium, magnesium, chloride, and calcium is weaker than it is in the body. This indicates that more water is lost in the sweat than electrolytes. So if the body lost more of its stored water but not as much of its electrolytes, what would happen to electrolyte concentration in the body? The concentration would increase. So during exercise when you dehydrate and lose electrolytes, their concentration in the body is greater than it was before you started to exercise. The body functions based on concentrations, not on absolute amounts. That alone presents a great problem for the argument that the cause of cramping is the loss of electrolytes that must be replaced.
So if dehydration or electrolyte loss through sweat doesn’t cause cramping, what does? No one knows for sure, but theories are emerging. Some researchers blame poor posture or inefficient biomechanics. Poor movement patterns may cause a disturbance in the activity of the Golgi tendon organs—“strain gauges” built into the tendon to prevent muscle tears. When activated, these organs cause the threatened muscle to relax while stimulating the antagonistic muscle—the one that moves the joint in the opposite way—to fire. There may be some quirk of body mechanics that upsets a Golgi device and sets off the cramping pattern. If that is the cause, prevention may involve improving biomechanics and regularly stretching and strengthening muscles that seem to cramp, along with stretching and strengthening their antagonistic muscles.
Another theory is that cramps result from the burning of protein for fuel in the absence of readily available carbohydrate. In fact, one study supports such a notion: Muscle cramps occurred in exercising subjects who reached the highest levels of ammonia release, indicating that protein was being used to fuel the muscles during exercise. This suggests a need for greater carbohydrate stores before, and replacement of those stores during, intense and long-lasting exercise.
When you feel a cramp coming on, there are two ways to deal with it. One is to reduce your intensity and slow down—not a popular option in an important race. Another is to alternately stretch and relax the affected muscle group while continuing to move. This is difficult if not impossible to do in some sports, such as running, and with certain muscles.
There is a third option that some athletes swear by: pinching the upper lip. Who knows—it may work for you the next time a cramp strikes.
Events in this duration include the Ironman-distance triathlon, double-century bike ride, and ultra-marathons in such sports as running, mountain biking, cross-country skiing, swimming, and kayaking. The stresses placed on the athlete can be extreme, with fatigue, heat, humidity, hills, wind, and currents taking their toll and gradually reducing performance. Nutrition is critical for these events.
Much of what was said in the previous section remains true here. The caveats are that solid foods now become a necessity, and hunger may well dictate what you decide to use for fuel. This might include bananas, cookies, jelly sandwiches, fruit juices, and soup. All of the foods selected should be toward the high end of the glycemic index. Otherwise, intake of carbohydrate, protein (especially branched-chain amino acids), and caffeine, as described above, may be continued.
These are the true “ultra” events of the world of endurance sports: the Race Across America (RAAM) and Paris-Brest-Paris bike races, double-Ironman-distance triathlon, Western States 100-mile run, and multiday bicycle racing tours such as the grueling Tour de France, the Vuelta a Espana, and the Giro d’Italia. It can be very difficult to take in adequate food and water, but for events done in daily stages, such as the Tour de France, daily nutritional intake between stages is often the difference between finishing and dropping out.
The longer the event, the more crucial it is that caloric needs be met by balancing nutrient intake with expenditure. Unsupported events require the athlete to carry nutrients or purchase them along the route, which makes planning all the more critical—the preferred sources must be light or generally available at convenience stores. Plan on taking in at least 6,000 calories daily—and that’s conservative. RAAM riders who spend at least 5 days riding across the United States, from the West to the East Coast, typically report 10,000-calorie days.
The longer the event, the lower the intensity, diminishing the relative amount of carbohydrate used as fuel. Whereas carbohydrate may account for 80 percent of the expended calories in events that last less than 90 minutes, it may contribute only about 50 percent of the total energy used in ultra-events. This means that the carbohydrate content of your fuel need not be as carbohydrate-rich as for shorter events. Conversely, protein intake becomes more important and should make up 5 to 15 percent of your fuel, so your nutritional source should reflect this demand. Not getting enough protein may well result in muscle wasting. That’s not conducive to good performance.
Fat also becomes more important in events of this duration. You’ll burn a lot of it, so it’s okay to take in a considerable amount—a fifth to a third of your fuel source—during the activity. In fact, ultra-marathoners often report a craving for fat during their events. Fat tends to present fewer gut problems during exercise than carbohydrate does, but that doesn’t mean it won’t affect your stomach at all. Before the event, be sure to experiment to discover the mix and types of fuels that work best for you.
Given the importance of refueling in events of this duration, it’s a good idea to closely examine all aspects of nutrition in great detail. Let’s start by considering the nutritional goals for the ultra-marathon athlete.
Replace all of the expended carbohydrate. Even at relatively slow velocities, a considerable amount of dietary carbohydrate is needed to delay the onset of fatigue while maintaining power. Carbohydrate should be taken in from the outset of exercise, using predominantly high glycemic index sources. It’s generally best that the sports drinks you choose have greater maltodextrin or glucose sources than fructose.
What changes from the previous discussions, however, is that the demand for carbohydrate relative to time is reduced. You’ll be using less fuel per hour while burning fewer calories from carbohydrate sources and more from fat than for short events, so the total replacement of carbohydrate is not as difficult as in shorter, faster events.
Prevent excessive dehydration while avoiding hyponatremia. Staying adequately hydrated for such events is critical. Once you are excessively dehydrated, it is difficult to get fluid levels back to normal. As always, use thirst as your guide to drinking. Hyponatremia is a threat to all athletes, including the faster ones, in events of this duration. The key, again, is drinking to satisfy thirst and not on a schedule. There will be a significant loss of body weight due to dehydration in each day’s activity in multiday events even while you are drinking to thirst. During rest and recovery times fluids should be consumed as desired.
Prevent central nervous system fatigue. Low levels of branched-chain amino acids in the blood during these long events can allow serotonin to enter the brain, causing the central nervous system to fatigue even though the other systems of the body are doing well. (See “What Is Fatigue?”)
Prevent muscle wasting. It is not unusual for athletes in ultra-distance events, such as the Tour de France, to lose several pounds, mostly from muscle. A study of trekkers in the Andes found that those who supplemented their diet with branched-chain amino acids gained muscle mass over 21 days, while their placebo-supplemented companions who otherwise ate the same diet lost muscle. Without adequate protein intake, the trekkers’ bodies were “cannibalizing” themselves. This helps us understand why, after ultra-marathon events, athletes look so gaunt. To prevent muscle catabolism, it is critical that the athlete take in protein along with carbohydrate during the race.
Prevent hunger. You will become quite hungry if you go 18 hours or longer with nothing more than sports drinks and gels. Foods including solid sources are a necessity, as they are more energy-dense than liquid sources. You’ll also find that after several hours, you become very tired of sweets and crave fat. Follow your desires and eat what sounds appealing, but consider these treats rather than main sources of fuel. The typical warnings still stand: Keep these foods low in fiber, and try them in workouts before using them in races.
The guidelines for including fat and protein (primarily branched-chain amino acids) now shift toward fat and protein and slightly away from carbohydrate. Your 300 to 600 calories hourly from carbohydrate, fat, and protein should be broken down, respectively, as 60 to 70 percent, 20 to 30 percent, and 10 to 15 percent. This proportion may enhance performance and recovery, while helping to prevent the serotonin buildup that can cause central nervous system fatigue and greater exertion.
Races of this distance often provide or allow support in the form of aid stations, feed zones, or even following support vehicles. This makes the replacement of huge energy needs throughout the event possible. For multiday events such as bicycle stage races, rest and recovery breaks are the times when the day’s caloric expenditures must be made up. During these times, which are essentially Stages IV and V of daily recovery, an assortment of foods such as potatoes, sweet potatoes, yams, vegetables, turkey sandwiches, fresh fruits, and soup will provide carbohydrate, fat, and protein.