Q: What is the best way to become heat-acclimated?
A: The best method for acclimating to the heat is to exercise aerobically in a hot environment.
For safety reasons, the initial exercise bouts may last as little as 10-15 minutes. Over time, however, as individuals acclimate to the physiological demands placed on them by heat, they can gradually increase the length of time that they exercise to 20-60 minutes per session.
The point to remember is that it takes most healthy people 10-14 days to fully acclimate to hot environments, although illness and alcohol consumption have been shown to slow the process.
Through this process, heart rate and body temperature at a given exercise intensity decrease, sweating rate increases, and sweat becomes more dilute. It has been estimated that as much as 25 percent of the apparently healthy population may be heat intolerant in an unacclimated state, with that number decreasing to about two percent after thorough acclimation.
It should also be noted that the benefits of heat acclimation are lost quite rapidly when an individual stops exercising in heat conditions. In general, with each two days of abstaining from heat exposure, one day of acclimation is lost. Thus, after three to four weeks without heat exposure, an individual should be considered unacclimated.
After even short periods without heat exposure (e.g., weekends or short periods of illness), risks during heat exposure due to de-acclimation can be substantial.
Source: Bryant, Cedric X. 101 Frequently Asked Questions about "Health & Fitness" and "Nutrition & Weight Control". Sagamore Publishing, 1999.
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