Keep Your Fitness Cool: Exercising in the Heat
Try these tips to work out safely when it's hot outside
In Phoenix, locals call it a "cold snap" when the thermometer drops
below 105 degrees. After spending time at a construction site, Arizona builder
Albert Ayala found his head swimming and noticed he had stopped sweating.
"I felt terrible," he recalls. He went home and a couple of hours
later, experienced fierce muscle cramps. "I thought I knew heat," he
says, "but it got me."
"It can happen to anyone," says Andrea M. McCauley, director of
communication for the American Red Cross in the Phoenix area. Although becoming
acclimated gradually to heat helps (in Phoenix, they say if you can get through
one summer, you won't notice the heat as much), acclimation is not the whole
How Hot Is Hot?
"When should you worry about exercising in the heat?" asks William
O. Roberts, MD, a sports medicine specialist with MinnHealth in White Bear
Lake, Minn., (not in a desert, notice -- this can happen anywhere). "That's
a moving target. A lot depends on the humidity. With no acclimation, 70 degrees
with high humidity can be dangerous. Your sweat can't evaporate."
Heat, Roberts repeats, is not something you can instinctively gauge.
"People often don't realize how hot and humid it is until they are already
If the body cannot carry the heat given off by exercising muscles to the
surface of the body fast enough -- and once it's there, if the surrounding air
is not cooler or evaporating sweat does not cool the body -- one's innards
literally stew, destroying and shutting down organ systems. It's not a matter
of discipline or will, it's a matter of heat exchange -- physics and
physiology, not physical endurance.
Symptoms of Trouble
The most common symptoms of heat illness are nausea, vomiting, headache,
weakness, or an altered mental state (confused, raving, aggressive, rambling
incoherently). Body temperature can spike up to 105 degrees or more (110 to 114
degrees is not unknown). If the sweating mechanism shuts down as it did in
Albert's case, over time the body loses all hope of cooling itself and the
brain and other organs begin to "cook." Heat stroke is the term for
this latter condition and can result in death.
But it's not that simple. "I usually don't want to say heat exhaustion
is a first stage of heat stroke or that it can go from one to the other,"
Roberts says. "They are two different things. You can get exercise
exhaustion in the heat, but it's usually from the exercise not the
Giving it a name is not that important. "You may suddenly get tired,
sick, headachy, thirsty, or faint," sums up McCauley.
Hydration Not the Whole Answer
The most common piece of advice about exercising in the heat is drink,
drink, drink -- water, not caffeine-loaded sodas or beer. Roberts says you can
get heat exhaustion even if you are hydrated, though. He recommends determining
your sweat rate instead and replacing that, without overdoing it.