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Question: How come you sweat when working out?
Humans are a homeothermic species; meaning that we regulate our core body temperature within a narrow range of values. Humans are capable of such tight regulation because of an elaborate system, which helps prevent death from hypothermia (low body temperature) and hyperthermia (elevated body temperature). Whether we workout or not, our muscles are part of this system that generates low heat on a continuous basis.
There are three different types of muscles that release heat upon contraction. The skeletal muscle is under voluntary control, while cardiac and smooth muscles are not. They are regulated by the autonomic nervous system (the nervous system that controls organ functions like digestion, hormone secretion and so forth). At rest 20-30% of heat is generated by involuntary muscle contraction such as in heartbeat and gastrointestinal peristalsis. Heat production (also known as thermogenesis) increases with a elevation in metabolic rate, which is the rate at which our cells (including muscle cells) use energy to function. Not all the energy results in work; some of it dissipates as heat. When one molecule of glucose is turned into carbon dioxide, water and energy (called ATP) through a chemical process called cellular respiration, 60% of the energy stored in the glucose molecule is released as heat.
It is important to let the heat dissipate to help regulate body temperature and prevent hyperthermia. When increased body temperature is detected by special sensors in the skin, the brain is signaled to stimulate the sweat glads to induce sweating. When sweat evaporates, it eliminates heat, which has a cooling effect on the body. It is worth noting that plastic sweat suits used for weight loss are dangerous, especially if worn in hot and dry weather because they prevent evaporation of sweat and the release of body heat.
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