ABSTRACT
Water is the major constituent of our human body, and it plays an essential role in body uid circulation, chemical reactions in energy metabolism, and excretion of waste products. In particular, the role for maintenance of body temperature is important during exercise. When the body temperature rises with elevating energy metabolism due to physical activity, sweating occurs in order to radiate heat, leading to loss of a large amount of water and electrolytes, such as sodium contained in body uid. This loss of body uid impairs thermoregulation and blood circulation, which leads to a decline in various physiological functions and can result in health problems, such as heat exhaustion and heat stroke. Therefore, to maintain homeostasis and avoid disorder, replenishment of water and electrolytes is necessary before and during or after exercise (American College of Sports Medicine et al. 2007). Individuals should drink 1.5 L of uid per 1 kg of body weight lost (due to water loss from exercise-induced sweating) to achieve rapid and complete recovery from dehydration. The general
33.1 Introduction ..........................................................................................................................609 33.2 Replenishment of Water ........................................................................................................609 33.3 Improvement of Energy Metabolism and Replenishment of Energy Substrates .................. 611 33.4 Building Muscle .................................................................................................................... 612 33.5 Maintenance of Exercise-Induced Homeostasis Disturbance .............................................. 614 33.6 Conclusion ............................................................................................................................ 615 References ...................................................................................................................................... 615
recommendation is to drink an isotonic or slightly hypotonic beverage that contains electrolytes, such as sodium, potassium, and chloride, at concentrations close to those in body uids (Castellani et al. 1998). In contrast, replenishment of water alone is not recommended for maintaining homeostasis of body uid in prolonged exercise that produces high sweat rates. Drinking water alone during prolonged exercise frequently leads to hyponatremia and a decrease in the osmotic pressure of body uids, which inhibits release of antidiuretic hormone, resulting in suppressed water intake and increased urine output (Takamata et al. 1994). During prolonged exercise lasting longer than 90 min, one should drink a uid containing electrolytes and carbohydrate to sustain carbohydrate oxidation and physical activity (Latzka and Montain 1999). Alternative methods to maintain body uid have been suggested, such as glycerol loading. This method prevents high temperatures and dehydration
FIGURE 33.1 Dietary strategy for improvement of exercise performance and tness. Exercise training improves physical performance, in that it builds muscle and enhances endurance. In addition, daily exercise is also important for prevention of lifestyle diseases and maintenance of tness with age. To obtain the effect efciently, we need to consider the amounts, types of nutrients, optimal timing, and combination of both macronutrients and microfood factors.
