Fatigue

High intensity activities: central fatigue is usually not involved in high intensity activities. Endurance activities: Central fatigue is a significant factor in many endurance sports caused by failure of neural transmission. The precise mechanism underlying the role of the CNS in causing, sensing and overriding fatigue is poorly understood.

High intensity activities: * depletion of energy sources (creatine phosphate and ATP) * increase in levels of the products of exercise such as lactate and hydrogen ions Endurance activities: * depletion of muscle and liver glycogen reserves * reduction in Ca2+ release * depletion of acetylcholine * dehydration, electrolyte loss, overheating