chapter  7
Macronutrient Intake during Endurance Activity to Optimize Performance
Pages 20

Competitive endurance sport activities place signicant metabolic demands on the body. For example, the energetic requirements during sustained endurance exercise may exceed 600 to 1,000 calories per hour in highly trained women and men. Providing for these caloric needs, and managing the associated disruptions in metabolic homeostasis, is essential for optimal performance and recovery from prolonged, heavy exercise. This chapter, specically, focuses on the role of nutrition during exercise to inŸuence metabolism and optimize performance for endurance athletes. For this purpose, endurance exercise is dened as any activity of approximately one-hour duration or longer (generally less than four hours), performed at moderate-to-vigorous intensities (approximately 50-85% VO2Max

7.1 Introduction .................................................................................................. 119 7.1.1 Substrate Utilization during Endurance Exercise ............................. 120

7.2 Carbohydrate Intake During Endurance Exercise ........................................ 121 7.2.1 Historical Perspective ....................................................................... 121 7.2.2 Effects of Carbohydrate on Metabolism and Performance .............. 123 7.2.3 Central Effects of Carbohydrate and Performance .......................... 125 7.2.4 Carbohydrate Amount, Timing, and Type ........................................ 126 7.2.5 Summary: Carbohydrate Intake during Endurance Exercise ........... 130

7.3 Fat Intake During Endurance Exercise ......................................................... 131 7.3.1 Metabolic and Performance Implications of Fat Intake ................... 131 7.3.2 Summary: Fat Intake during Endurance Exercise ............................ 133

7.4 Protein/Amino Acid Intake during Endurance Exercise .............................. 133 7.4.1 Branched-Chain Amino Acids ......................................................... 134 7.4.2 Individual Amino Acids ................................................................... 135 7.4.3 Intact Proteins and Protein Hydrolysates ......................................... 135 7.4.4 Summary: Ingestion of Protein/Amino Acids during Endurance

Exercise ............................................................................................. 137

[maximum oxygen consumption]). Our scope is limited to the inŸuences of energyproviding nutrients (carbohydrate, protein, and fat) consumed during exercise and particularly how deviations in temporal administration may inŸuence resulting performance, recovery, and so on. Due to the universal role the macronutrients have on various physiological processes, similarities between pre-, during-, and postexercise recommendations are expected and unavoidable. However, it is our contention, as with many of the contributors of this book, that each individual athlete and sporting scenario are different, and for this reason, strategies from one area may not apply for one athlete but will apply for another. In addition, macronutrient consumption during endurance exercise is usually accompanied by water/ electrolyte intake, as athletes consume much of their caloric intake during exercise from sports beverages, which deliver these constituents simultaneously. Thus, readers are referred to reviews from other sources regarding Ÿuid and electrolyte intake during endurance exercise (Noakes 1993; Rodriguez et al. 2009a; Sawka et al. 2007; Shirreffs 2009).