The body regulates temperature during physical activity primarily through sweating and increased blood flow to the skin. As muscles produce heat during exercise, the hypothalamus detects this rise in temperature and signals sweat glands to produce sweat, which cools the body down as it evaporates. Meanwhile, to dissipate heat, blood vessels in the skins dilate, increasing circulation and allowing more heat to escape. Proper hydration is crucial to maintain this thermoregulation process and prevent overheating or dehydration during physical exertion.