Exercise physiology loss of integrity to the blood brain barrier. Hyperthermia also can lower cerebral blood flow, and raise brain temperature. Researchers once attributed fatigue to a build-up of lactic acid in muscles. However, this is no longer believed. Rather, lactate may stop muscle fatigue by keeping muscles fully responding to nerve signals. The available oxygen and energy supply, and disturbances of muscle ion homeostasis are the main factor determining exercise performance, at least during brief very intense exercise. Each muscle contraction involves an action potential that activates voltage sensors, and so releases Ca ions from the muscle fibre’s sarcoplasmic reticulum. The
Anaerobic exercise performed for longer periods of time. Activities such as walking, long slow runs, rowing, and cycling require a great deal of oxygen to generate the energy needed for prolonged exercise (i.e., aerobic energy expenditure). In sports which require repeated short bursts of exercise however, the anaerobic system enables muscles to recover for the next burst. Therefore, training for many sports demands that both energy producing systems be developed. The two types of anaerobic energy systems are: 1) high energy phosphates, adenosine triphosphate and creatine phosphate; and 2) anaerobic glycolysis. The former is called "alactic anaerobic" and the latter "lactic anaerobic"