The Science of Sweat
Sweating doesn’t do much to remove toxins from the body, but it is the body’s most important avenue for heat loss during physical activity and heat exposure. But there is a price to be paid for sweating and that price is dehydration, unless enough fluid is consumed to offset sweat loss.
- Contrary to popular belief, sweating is not an effective way of removing toxins from the body, unless you consider body heat a toxin.
- During vigorous physical activity and heat exposure, sweating is the most effective way for the body to shed heat and maintain a safe internal (core) temperature.
- The greatest concentrations of sweat glands are on the hands, feet, back, and chest.
- The body quickly loses heat whenever sweat evaporates from the skin.
- Sweating begins whenever core temperature exceeds the sweat threshold. In other words, an increase in body temperature turns on sweating. (Skin temperature also contributes to this response.)
- As physical fitness improves, sweat loss increases. Fit athletes have to become better drinkers during exercise to compensate for increased sweat losses.
- During physical activity, heat-acclimated people sweat sooner, sweat more, have larger sweat glands, and their sweat is spread over a larger portion of the skin.
- The risk of heat illness is greater in unfit, unacclimated people in part because their bodies heat up more before sweating begins.
- Sweat contains dozens of minerals, amino acids, and metabolites, but the largest constituents of sweat are sodium and chloride, the reasons for sweat’s salty taste.
- Potassium is lost in sweat, but in very small quantities. For that reason, athletes should consume sports drinks and salty snacks after prolonged exercise rather than bananas and oranges.
- Despite its many components, sweat is over 99% water.
- Humans are born with 2 – 4 million sweat glands.
- Even newborn babies have the capacity to sweat.
- Puberty increases the number of active sweat glands.
- Sympathetic nerves cluster around the coil of the sweat gland. When stimulated, the nerves release acetylcholine, the neurotransmitter that stimulates the glands to secrete sweat.
- Dehydration reduces sweating as the body attempts to conserve body fluids.
- Sweat is less salty in fit, acclimated people because their sweat glands conserve salt to help maintain blood volume during exercise. However, because sweat rates are greater in fit people, overall sodium loss often remains unchanged.
- The capacity to sweat is determined by genetics, fitness, and heat acclimation.
- Clothing and equipment impede heat loss by reducing the evaporation of sweat.
- Eccrine sweat glands are activated during physical activity. Apocrine sweat glands (in the armpits and elsewhere) are activated by catecholamines (not acetylcholine) during emotional stress.
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