Anaerobic exercise requirements

The influence of physical activity on nutritional requirements and health is not the same for all activities. For the purposes of this book, exercise will be classified as either anaerobic or aerobic activities. These terms provide descriptive information about both the level of exertion and the duration of the activity and are useful in relating activities to nutritional needs. Anaerobic exercise includes activities such as wei tlifting and sprinting, and involves maximum exertion for periods of time less than 1 or 2 minutes. Aerobic activities are performed for periods usually in excess of 15 minutes at less than maximum speed or strength. 

Some of the responses by the body to anaerobic exercise are visually obvious. Greater strength, speed, and muscle development are reasons that athletes emphasize anaerobic training. However, research has shown that these results are not easily predicted, and even the effects on the amouit of muscle mass are not entirely clear (9). The effects of these short-duration exercises on cardiopulmonary function and on nutritional requirements are minimal. 

Oral creatine supplements first gained popularity among athletes in the early 1990s following the publication of a Karolinska Institute study that found that subjects who took creatine supplements experienced a significant increase in total muscle creatine content. In theory, increased creatine stores would increase PCr stored in the muscles, which would in turn provide a larger power supply for anaerobic muscle activity and exercise (short bursts of exercise which don t require oxygen). 

Glycolysis produces energy. Michael Johnson sprints to another victory in the 200-meter semifinals of the Olympics. Johnson, like anyone who sprints, requires a source of energy that can be rapidly accessed. The anaerobic metabolism of glucose the process of glycolysis provides such a source of energy for short, intense bouts of exercise. [Simon Bruty/ Allsport.]... 

Double-blind placebo-controlled studies of oral supplementation of creatine in human subjects have shown increased performance during short duration, strenuous, high-intensity exercise. Such activities require that ATP be replenished rapidly from phosphocreatine stores during anaerobic metabolism. These studies usually consisted of ingestion of 20 g of creatine per day for 5 days followed by a maintenance dose of 5-10 g/day. Studies on creatine as an ergogenic aid have not been uniformly positive some have shown no beneficial effect and still others have been equivocal and indicated that creatine supplementation did not enhance athletic activities. The safety issues of long-term creatine supplementation on kidney, liver, nerve, muscle, and other tissues are not known. 

Both respiration rate and tidal volume (the amount of air moved per breath) increase with exercise, but above the anaerobic threshold the tidal volume no longer increases (remains at about 2 to 2.51). From that point, increases in ventilation require greater increases in respiration rate. A similar limitation occurs for stroke volume in the heart (limited to about 120 ml). 

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