Dietary Adequacy

Low glycogen stores reduce the time an athlete is capable of exercising, a fact that mandates the regular consumption of carbohydrates to maintain or replace limited glycogen stores.¹² This requires, ideally, a carbohydrate intake of between 7 and 10 grams per kilogram of body weight per day.

The timing of carbohydrate ingestion is also important and may influence glycogen storage and resynthesis. A study of highly trained male cross country runners found that food intake was generally adequate and well timed except for the period after competition. Although it is recommended that endurance athletes consume carbohydrates immediately after competition to encourage restoration of glycogen stores, these athletes delayed eating carbohydrate foods until, on average, 2.5 hours after competition.¹³ A delay of this magnitude leads to poor glycogen replacement, and subsequent days of exercise showed the negative effect of reduced endurance. A study of marathon runners found that a significant proportion of total energy intake occurs after 4:00 P.M. rather than earlier in the day when it's needed the most.¹⁴ Delayed eating represents a missed opportunity for trained endurance athletes to maximize muscle glycogen storage after exercise.^15,16

There is no substitute for consuming sufficient energy and carbohydrates for endurance events. Supplements and ergogenic aids appear to be ineffective. The only strategy that works effectively is to eat enough and to eat at a time that is most useful for delivering energy to needy muscles or for maximizing glycogen storage. There is also evidence that endurance athletes must focus on glycogen storage activities about 1 week before a major competition.¹⁷ A failure to do so can have a negative effect on the athlete's endurance capacity.

Endurance athletes, because of the time spent training and competing, may need to develop their own strategies for obtaining energy and fluids during the activity. This is not easy because consuming the wrong foods or fluids or consuming them at the wrong time will have a performance-decreasing effect. The “nervous stomach” many athletes experience just before a race makes the consumption of the right energy or fluid package even more difficult. Athletes should undergo a purposeful experimentation to discover what sports beverages, carbohydrate gels, and other sources of energy and nutrients are well tolerated so they can use this information to optimize training sessions and achieve peak performances during competitions. The reliance on recommendations for the general athlete population may be a good starting point, but it is not enough to generate winning performances in tough competitive fields.

Each type of race alters slightly the proportion of carbohydrate and fat that is burned as fuel (more intensity equals proportionately more carbohydrate; lower intensity equals proportionately more fat), but it's the carbohydrate level that ultimately determines if the athlete will “hit the wall.” That is, when the glycogen stores are depleted, the athlete will no longer be capable of maintaining a sufficiently strong pace. Since endurance events are long, every available opportunity must be capitalized on to ensure that the athlete has enough food energy to continue the race and to store enough energy (glycogen) to do well during the next day of racing.

Athletes should do whatever is necessary to take in sufficient energy and nutrients (bringing baggies filled with food to meetings, eating while walking to class, snacking while going to the car), or the benefits derived from training will be wasted. Athletes who do not eat effectively become more easily fatigued and injured and are more likely to try unproven products touted as having ergogenic properties. There is no doubt whatsoever that much of the attention given to ergogenic aids and nutrient supplements by athletes, whether they've cyclists, runners, or swimmers, is to overcome a failure in planning to eat enough and to eat on time.

Maintaining hydration status is important for operating at optimal physiological levels of efficiency. Endurance athletes should practice consuming fluids frequently, even in the absence of thirst, to reduce the chance of dehydration. Consumption of a carbohydrate-containing beverage with small amounts of sodium is useful for fluid absorption and for maintaining the drive to drink.

Nutrient Supplementation

Nutritional Concerns for Female Endurance Athletes