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
Oxygen is doubted; a placebo effect is a more likely explanation. Available studies support a performance boost from oxygen enriched mixtures only if it is breathed "during" aerobic exercise. Other recreational uses that do not involve breathing include pyrotechnic applications, such as George Goble's five-second ignition of barbecue grills. Smelting of iron ore into steel consumes 55% of commercially produced oxygen. In this process, is injected through a high-pressure lance into molten iron, which removes sulfur impurities and excess carbon as the respective oxides, and . The reactions are exothermic, so the temperature increases to 1,700 °C. Another 25% of commercially