Florida Death Row Advocacy Group

Human bodies dissipate heat by varying the rate and depth of blood circulation, by losing water through the skin and sweat glands, and - as the last extremity is reached - by panting, when blood is heated above 98.6 degrees. The heart begins to pump more blood, blood vessels dilate to accommodate the increased flow, and the bundles of tiny capillaries threading through the upper layers of skin are put into operation. The body's blood is circulated closer to the skin's surface, and excess heat drains off into the cooler atmosphere. At the same time, water diffuses through the skin as perspiration. The skin handles about 90 percent of the body's heat dissipating function. Sweating, by itself, does little to cool the body unless it is removed by evaporation.  If the relative humidity is high, then the evaporation of sweat will be minimized. The evaporation process itself works this way: the heat energy required to evaporate the sweat is extracted from the body, thereby cooling it. Under conditions of high temperature (above 90 degrees) and high relative humidity, the body is doing everything it can to maintain 98.6 degrees inside. The heart is pumping a torrent of blood through dilated circulatory vessels; the sweat glands are pouring liquid - including essential dissolved chemicals, like sodium and chloride - onto the surface of the skin.

Too Much Heat

Heat disorders generally have to do with a reduction or collapse of the body's ability to remove heat by circulatory changes and sweating, or a chemical (salt) imbalance caused by too much sweating. When heat gain exceeds the level the body can remove, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body's inner core begins to rise and a heat disorder may develop. Ranging in severity, heat disorders share a common feature: the individual was over-exposed and/or over-exerted, given the existing heat situation. More so, sunburn can significantly add to the problem by retarding the skin's ability to shed the excess heat. Studies indicate that, other things being equal, the severity of heat disorders tend to increase with age (the same heat situation might yield heat cramps in a 17 year old, heat exhaustion in someone 40, and heat stroke in a person over 60).

Interestingly, the human body does have the ability to acclimate. This means that your body attempts to adjust to the climate in which you live. This means that the average healthy person living in Florida can better deal with heat stress than the average healthy person living in Michigan (but, conversely, the Michigan person would better handle cold stress). This can be seen on a seasonal basis too, since your body chemistry adjusts to warmer weather as summer wears on. In general, acclimatization has to do with the body adjusting its sweat-salt concentrations, among other things. It seeks to adjust the amount of stored water necessary to effectively regulate body temperature, without disturbing the chemical balance.

Heat disorders generally have to do with a reduction or collapse of the body's ability to shed heat by circulatory changes and sweating, or a chemical (salt) imbalance caused by too much sweating. When heat gain exceeds the level the body can remove, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body's inner core begins to rise and heat-related illness may develop. Ranging in severity, heat disorders share one common feature: the individual has overexposed or overexercised for his age and physical condition in the existing thermal environment. Sunburn, with its ultraviolet radiation burns, can significantly retard the skin's ability to shed excess heat. Studies indicate that, other things being equal, the severity of heat disorders tend to increase with age - heat cramps in a 17-year-old may be heat exhaustion in someone 40, and heat stroke in a person over 60. Acclimatization has to do with adjusting sweat-salt concentrations, among other things. The idea is to lose enough water to regulate body temperature. with the least possible chemical disturbance.