The Mystery of Sweating Buckets
Q&A
Q. A 90-degree day means I sweat buckets just walking the dog and lose every bit of energy. Why do some people tolerate the heat less well than others?
A. The overlapping factors that affect an individual’s heat tolerance are almost incalculable, ranging from age, body mass and percentage of body fat to metabolism rates, circulatory efficiency and hydration. Thermoregulation also involves the brain, nerves and hormones.
Then there are medical conditions that can reduce heat tolerance, such as menopause, autoimmune diseases, multiple sclerosis, thyroid trouble and cancer of the pituitary gland, not to mention some drugs used to treat diseases. Anxiety is often a factor, as is the overuse of common substances like caffeine.
On top of all these variables, studies have found that tolerance cannot be considered without taking into account other circumstances, like the intensity of exercise and the level of humidity. For example, humidity determines whether sweating and evaporative cooling can help ease the effects of vigorous exercise in high heat.
Studies done for NASA and the military have found that systematic and gradual exposure to activity at high heat can lead to acclimation and physiological changes that help the body cope better. As with so many other conditions, common sense is essential, and people who are heat intolerant are advised to seek cooler temperatures and drink plenty of liquids. question@nytimes.com
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