Chapter 23: Nutrition, Body Composition, and Performance

OBJECTIVES

By studying this chapter, you should be able to do the following:

1. Describe the effect of various carbohydrate diets on muscle glycogen and on endurance performance during heavy exercise.

2. Contrast the “classic” method of achieving a supercompensation of the muscle glycogen stores with the “modified” method.

3. Describe some potential problems when glucose is ingested immediately prior to exercise and how these problems can be avoided.

4. Describe the importance of blood glucose as a fuel in prolonged exercise and the role of carbohydrate supplementation during the performance.

5. Explain why multiple carbohydrates have to be consumed during prolonged exercise when blood glucose is used at a very high rate.

6. Describe the need for protein during the adaptation to a new, more strenuous exercise level with the protein need when the adaptation is complete.

7. Describe the recommended range of protein intake for athletes, and indicate dietary factors that would demand using the top end of the range.

8. Describe the recommended fluid replacement strategies to use before exercise, during exercise of different durations, and following exercise.

9. Describe the salt requirement of the athlete compared to that of the sedentary individual and the recommended means of maintaining sodium balance.

10. Provide a brief summary of the effects of vitamin supplementation on performance.

11. Characterize the role of the precompetition meal on performance and the rationale for limiting fats and proteins.

12. Explain why one must be careful in recommending specific body fatness values for individual athletes.

OUTLINE

• Carbohydrate 526

  • Carbohydrate Diets and Performance 526

  • Carbohydrate Intake Prior to or During a Performance 528

  • Carbohydrate Intake Post-Performance 532

• Protein 532

  • Protein Requirements and Exercise 532

  • Protein Requirements for Athletes 534

• Water and Electrolytes 535

  • Fluid Replacement—Before Exercise 535

  • Fluid Replacement—During Exercise 536

  • Fluid Replacement—After Exercise 538

  • Salt (NaCl) 538

• Minerals 540

  • Iron 540

• Vitamins 541

• Precompetition Meal 541

  • Nutrients in Precompetition Meal 542

• Body Composition and Performance 542

KEY TERMS

glucose polymer

supercompensation

INTRODUCTION

This chapter on nutrition, body composition, and performance is an extension of Chap. 18 because the primary emphasis must be on achieving health-related goals before performance-related goals are examined. In fact, the information presented here must be examined in light of what the average person needs. Does an athlete need additional protein? What percentage of body fat is a reasonable goal for an athlete? We will address these questions in that order. For a more detailed look at these issues, see Suggested Readings for Clinical Sports Nutrition by Burke and Deakin, Nutrition for Health, Fitness and Sport by Williams, Anderson, and Rawson, and the 2016 ACSM position stand on Nutrition and Athletic Performance.

In Chap. 18, we indicated the recommended range of nutrient intakes:

• Adults should get 45%–65% of their calories from carbohydrates, 20%–35% from fat, and 10%–35% ...