The Paleo Diet for Athletes (8 page)

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.

EATING DURING 90-MINUTE TO 4-HOUR EVENTS

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.

LACTIC ACID’S BAD RAP

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.

EATING DURING 4- TO 12-HOUR EVENTS

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.

WHAT CAUSES MUSCLE CRAMPS?

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.