Play it safe in hot, humid
weather — it can overheat the heart.
The human body is built for heat. It works best at an internal
temperature of 98 degrees fahrenheit and has intricate mechanisms
to maintain that temperature. Yet hot weather, especially those
triple-H days — hazy, hot, and humid — can strain the heart and
Your cells produce heat in the process of converting sugar to
energy. When the air temperature rises, your body doesn't have
the option of generating less heat. You can shed clothes, but you
can't get past your birthday suit. That leaves two main ways to
offload heat: radiation and evaporation.
As things heat up, temperature sensors in your body tell blood
vessels in the skin to relax and accept more blood. This
peripheral blood flow radiates heat to the cooler skin, which
passes it on to the air. But this solution no longer works when
the air temperature approaches body temperature.
Sweating is another way of self-cooling. It uses heat from the
body to turn liquid sweat into water vapor (by evaporation).
Evaporating just 2 teaspoons of sweat could cool your bloodstream
by two degrees. Sweating works well on dry days, but as the
humidity climbs above 75% or so the amount of water in the air
makes evaporation increasingly difficult.
Heat and the heart
Radiation and sweating each put pressure on the heart. Rerouting
blood to the skin forces the heart to work harder. On a hot day,
it may move four times as much blood as it does on a cool day.
Sweating can steal minerals from the bloodstream that are needed
to maintain a healthy fluid balance.
These stresses pass unnoticed in healthy people. But they can
cause trouble in those with cholesterol-clogged arteries or
cardiac muscle damaged by a heart attack or weakened by heart
disease. Hot weather can be problematic for people taking a beta
blocker or diuretic (water pill), or those who have Parkinson's
disease, diabetes, a stroke, or another condition that can dull
the brain's response to dehydration. It also tends to worsen
conditions like heart failure, emphysema, or kidney failure.
Beat the heat
Common sense and a bit of vigilance can help you weather hot,
Find your cool. Chilled air is the best
way to beat the heat. If you don't have an air conditioner, spend
an hour or two in a movie theater, at a store, or with an
air-conditioned neighbor. A cool shower or bath, or putting a
cold, wet cloth or ice pack under your arms or on your groin can
also help. A fan can speed evaporation, but only if the air is
cooler than you are.
Drink up. Maintaining your body's fluid
level helps fight overheating. Unfortunately, this isn't easy for
everyone. Stomach or bowel problems, a faulty thirst signal,
diuretics, physical activity, or low fluid intake can all
contribute to dehydration. On dangerously hot and humid days, try
downing a glass of water every hour. (If you have heart failure,
check with your doctor or nurse first.) Go easy on sugary soda
and full-strength fruit juice since they slow the movement of
water from the digestive system to the bloodstream. Cut back on
caffeinated beverages and alcohol, or skip them altogether,
because they can cause or amplify dehydration.
Slow down. Try not to exercise or do
other physical activity when the air temperature and humidity are
high. Evening and early morning are best. If you do exercise,
drink more healthful beverages than usual.
Eat light. Choose smaller meals that
don't make your digestive system work as hard. Cold soups,
salads, and fruits can satisfy your hunger and give you extra
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