Topic 9

A reversible, exercise-induced decline in performance.

Limit to: * peripheral fatigue—develops rapidly and is caused by reduced muscle cell force * central (or mental) fatigue—develops during prolonged exercise and is caused by impaired function of the central nervous system.

High-intensity exercise involves a vigorous bout of intense activity that may last for less than a second, or as long as 1–2 minutes, for example, some types of interval training, plyometrics. The major sources of energy for this are derived from anaerobic processes. Endurance activities involve prolonged sessions of low-intensity activity that may last from several minutes to several hours, for example, leisure cycling or jogging. The major sources of energy for endurance activities are aerobic processes.

Fatigue is perceived differently by individual athletes and may depend on multiple factors such as age, level of fitness and the specific type of activity or exercise carried out. On a physiological level, the development of peripheral fatigue in high-intensity activities depends on the rate of: • depletion of energy sources (creatine phosphate and ATP) • increase in levels of the products of exercise such as lactate and hydrogen ions. The physiological causes of peripheral fatigue in endurance activities include: • depletion of muscle and liver glycogen reserves • reduction in Ca2+ release • depletion of acetylcholine • dehydration • electrolyte loss • overheating. Central (mental) fatigue is a significant factor in many endurance sports caused by failure of neural transmission.

Different aspects of recovery can occur at different rates, and recovery rate also depends on the type of activity (high-intensity, team sports or endurance). Include: * excess post-exercise oxygen consumption (EPOC) for: – restoration of muscle creatine phosphate stores – removal of lactic acid – replenishment of myoglobin stores * replacement of muscle and liver glycogen stores. Link to option A: Optimizing physiological performance