Nutrition Tactics for Sports Requiring Power and Endurance

This chapter provides nutrition information for sports where athletes have intermittent bouts of high-intensity activity followed by periods of lower-intensity activity. Team sports such as basketball, volleyball, rugby, team handball, and soccer all have combinations of high-intensity and lower-intensity activity interspersed throughout the competition. The mixed intensity of certain individual sports, such as figure skating and tennis, may also fall into this category. This differs from other sports, where the focus is either predominantly endurance or predominantly power or speed. There is nothing in artistic gymnastics training or competition that requires, for instance, a great deal of aerobic endurance; and marathon runners rarely require the explosive power exhibited by gymnasts. Team sport athletes must focus on speed, power,andendurance. Soccer players must run the field at a controlled pace until a sudden opening requires a quick burst of speed. Basketball players may jog back and forth in a steady aerobic pace, but each player must have the capacity for a powerful jump to grab a rebound or for a quick sprint to make a defensive play.

The intermittent high and low intensity of team sports creates a requirement for energy that is derived from a combination of aerobic and anaerobic means. Although the anaerobic metabolic processes are solely reliant on existing stores of ATP, phosphocreatine (PCr), and muscle glycogen, the aerobic processes derive energy from muscle glycogen, blood glucose, fat, and to a lesser extent, protein. There is a heavy reliance on muscle glycogen for the majority of muscle energy during team sport activity, with nearly an equal reliance on fat and blood glucose for most of the remaining source of energy. Fat is almost never in short supply. However, the amount of glucose energy in blood is small and requires constant vigilance by the athlete to ensure a continuing source of glucose during the competition.

The heavy reliance on muscle glycogen and blood glucose to fulfill the energy needs of working muscles demands a high level of consumed carbohydrates before exercise and carbohydrate-containing sports beverages during exercise. In a study of the performance outcomes of a moderate (39 percent of total calories) versus high (65 percent of total calories) carbohydrate intake, the higher-carbohydrate diet significantly improved intermittent exercise performance.¹

Repeated sprint work is enhanced by consumption of a carbohydrate-electrolyte beverage.² Although it has been long established that consumption of a carbohydrate-electrolyte beverage enhances submaximal endurance performance, only recent studies have clearly shown the benefits of these beverages during high-intensity, short-duration efforts such as those found in football and basketball. Subjects performed seven additional 1-minute cycling sprints at 120 to 130 percent of peak VO₂when they consumed a 6 percent carbohydrate-electrolyte beverage, as compared with a water placebo. This finding suggests that a dramatic improvement in sprint capability during the last 5 to 10 minutes of a basketball game is possible if players methodically consume a sports beverage.

A similar study determined that sports drinks (i.e., carbohydrate-electrolyte beverages) can help maintain high-intensity efforts during high-intensity activities consisting of intermittent sprinting, running, and jogging.³ Again, these findings have strong positive implications for sustaining high-intensity activity over the course of a typical basketball or soccer game.

The effects of consumption of the individual components of a sports beverage (electrolytes, water, or carbohydrate) and of the combination of all components have also been assessed. Compared with the electrolyte-only trial, performance during the water-only and carbohydrate-only trials was approximately 6 percent faster. However, the combination of carbohydrate and water caused a performance enhancement that was approximately 12 percent faster than the electrolyte trial and 5 to 6 percent faster than when water only or carbohydrate only were consumed.⁴ These findings support the thesis that carbohydrate enhances water absorption and that the limited carbohydrate storage mandates consumption of carbohydrate during exercise. The high demands on circulating and stored carbohydrate during high-intensity work require a constant vigilance to ensure proper and speedy replacement. This study was based on earlier work that showed exercise performance improved significantly with carbohydrate feedings.⁵ It has also been found that the optimal level of carbohydrate concentration during exercise is 6 to 7 percent. This concentration is best for fluid absorption and also helps to efficiently deliver carbohydrate. An 8 percent carbohydrate solution causes a slower fluid absorption.⁶

A basketball player leaping for the ball and a soccer player sprinting toward the ball and jumping high to kick it are activities comparable to certain forms of strength training. A study of resistance-trained athletes found that athletes tended to perform more repetitions of the same weight when carbohydrate was consumed versus a water placebo. Blood glucose and lactate concentrations were higher with the carbohydrate trial, suggesting that more carbohydrate was available and used to sustain the high-intensity exercise.⁷ A study of head-to-head comparisons of Gatorade, Powerade, and All Sport found that Gatorade stimulates fluid absorption faster than either Powerade or All Sport.⁸ This difference can be attributed to both the type of carbohydrate and the concentration of carbohydrate in the beverages. Gatorade has a carbohydrate concentration level that is consistent with the positive findings in virtually all the studies (6 percent) and contains an equal mixture of sucrose and glucose. Powerade and All Sport have higher carbohydrate concentrations, mainly from fructose. Fructose has been shown to cause gastrointestinal (GI) distress; it is also less efficient in sustaining blood glucose because it requires a secondary conversion in the liver after absorption.

Athletes who perform repeated or sustained high-power efforts experience a reduction in performance when they are dehydrated.⁹ A 6 percent carbohydrate solution aids in fluid delivery, a fact that should be considered when team sport athletes select a rehydration beverage.

Several general nutrition guidelines-covering what to do before, during, and after exercise and competition-are important for virtually all athletes involved in sports that have intermittent periods of maximal intensity.

The two keys to these guidelines are fluids and carbohydrates in the context of a generally varied diet. Athletes should explore workable strategies to consume both fluids and carbohydrates at every opportunity. Recent findings tend to contradict the traditional and commonly followed belief that carbohydrate-containing beverages are useful only for endurance (aerobic) activities lasting longer than 60 minutes. The best predictors of athletic performance are maintenance of blood volume and maintenance of glycogen and glucose. What follows are some strategies that might be useful for achieving both enhanced hydration and improved maintenance of system carbohydrate in different sports.