ABSTRACT
The importance of carbohydrate as a substrate for skeletal muscle during exercise has been known since the turn of the twentieth century. At this time, evidence was provided to show that both carbohydrate and fat contributed as energy sources for the muscle during submaximal aerobic exercise, but as exercise intensity increased, carbohydrate-based fuels (i.e., muscle and liver glycogen, blood glucose, lactate) predominated. A series of experiments undertaken in the 1920s provided perhaps the rst information on the interaction of diet and exercise on substrate metabolism and exercise capacity. The results from these studies conrmed that carbohydrate and fat were oxidized by the muscle during submaximal exercise; that an individual’s preceding diet inŸuenced muscle metabolism both at rest in the postabsorptive state and during subsequent exercise. Further, with an increase in the relative intensity of exercise, there was a shift from utilization of fat as a fuel source toward
6.1 Introduction and Background ....................................................................... 107 6.2 Muscle and Liver Glycogen Stores in Humans ............................................. 108 6.3 Preexercise Nutrient Timing ......................................................................... 109
6.3.1 The Week Prior to Competition: Carbohydrate Loading Strategies ....109 6.3.2 The Day Prior to Competition .......................................................... 111 6.3.3 Immediate Precompetition Feeding Strategies................................. 111 6.3.4 Preexercise Nutrient Intake: Timing-What Do We Know? ........... 112 6.3.5 Is the Glycemic Index of a Preevent Meal Important? ..................... 114 6.3.6 Should the Preexercise Meal Contain Fat or Protein? ...................... 114 6.3.7 How Much Carbohydrate? ................................................................ 115 6.3.8 Is the Preexercise Meal Required If Athletes Consume
Carbohydrate during Exercise? ......................................................... 115 6.4 Summary and Guidelines for Preevent Feeding ........................................... 115 6.5 Examples of Useful Preexercise Meals or Snacks ........................................ 116
carbohydrate-based fuels, and that individuals have a low tolerance for exercise when the diet preceding exercise is low in carbohydrate (i.e., high in fat). Classic work from researchers in Scandinavia in the 1930s further described how diet, training, and exercise intensity/duration affected carbohydrate and fat utilization. The ndings from these early pioneering studies were instrumental in underpinning our current understanding of muscle fuel metabolism and laid the foundation for many of the modern-day studies of exercise-nutrient interactions (Kiens and Hawley 2011).
