When I exercise I sweat a lot; does this mean I'm out of shape?
Actually, it means you are in better shape than if you didn't sweat very much. To really appreciate the answer to this
question, it's helpful to know a little bit about sweat glands. There are two types of sweat glands. One is found primarily
around the armpits and genitalia, and these glands release a fatty secretion that gives a characteristic odor when the sweat
interacts with skin bacteria. This sweat gland doesn't become fully operational until adolescence. The other sweat gland covers
most of the body and secretes essentially an odorless sweat that accounts for most of the evaporative cooling.
When you exercise, your body produces a lot of metabolic heat; much of it coming from your body's core rather than the
extremities. A heated muscle is typically more functional, but when the temperature gets too high serious, life threatening
tissue damage may occur. In response to an elevated core temperature, the brain signals the body to dissipate the excess
heat as rapidly as possible through sweat glands. Air temperature is directly related to the rate of sweating. Sweat is
transported to the skin so that it can evaporate and create a cooling effect. Evaporation provides the greatest protection
against over heating. Moreover, as the environmental temperature increases the body's ability to lose heat from other sources
decreases, and when the environmental temperature exceeds body temperature, heat is gained. At this point the only substantial
way to dissipate heat is through evaporation.
Sweat is only effective for cooling if it evaporates. Sweating alone does not cool the skin. If humidity is high, the
rate of evaporation may be greatly reduced or prevented resulting in the sweat remaining in a fluid state. If the sweat remains
on the skin it can further heat the body by acting as an insulator. Sweat dripping profusely off the skin may be an indicator
that the humidity of the environment is so high that sweat can't evaporate. This can cause your body to get too hot. Wearing
too many clothes, such as running in sweats in the summer months, can also trap sweat and overheat your body. Since cooling
occurs with evaporation, it is best not to wipe off your sweat.
Effective evaporation is also limited by lack of air movement. During exercise the air surrounding the body may become
saturated with water acting as a zone of insulation. If this warm air is replaced by cooler air from the wind on a breezy
day or a fan heat loss is increased as the moving air takes the heat away. Air currents of 4 mph are twice as effective as
air currents of 1 mph, which is the basis of the wind chill index. This explains why using fans and wearing fewer clothes
or those that wick sweat are desirable on a hot day.
So to the question, men and women who are conditioned respond better to heat stress than sedentary people. Trained people
sweat sooner at lower body temperatures, they sweat more, and their sweat is more diluted. Training actually changes the sweat
glands and causes an increase in plasma volume that is essential in the production of sweat and for other cardiovascular and
thermoregulation demands. All of this allows a trained person to store less heat and therefore have a lower core temperature
than an untrained person.
My wife when exercising doesn't sweat as much as I do and her sweat seems to glisten how can that be?
Women tend to regulated their body temperatures differently compared to men. They produce smaller sweat droplets that
adhere to the skin better than large droplets allowing greater absorbtion of heat and therefore more heat is dissipated when
the sweat is evaporated. Men's sweat droplets are larger and tend to drop off before being evaporated limiting absorbtion