Summer heat can turn refreshing outdoor exercise into a sweat-drenched experiment in heat exhaustion.
Overheating, the mild form, causes fatigue and dizziness. That’s annoying enough. As internal temperatures rise above 100 degrees, athletes may experience cramps, headaches, nausea and vomiting. By the time core temperatures reach 104, the body rebels from hyperthermia.
If the athlete keeps on pushing and internal temperatures pass 104, the athlete risks “organ failure and death from heat stroke,” said Dr. Aurelia Nattiv, a sports medicine professor at the University of California, L.A.
Scientists are learning more about the factors that influence overheating — and ways to help an athlete avoid it. Just how hot and bothered you get on the inside depends on a number of factors: body size, fitness level, intensity of exercise, the heat and humidity of the environment and how acclimatized you are to exercising in hot weather.
Follow the advice here and those outdoor runs can still be a pleasant — if unavoidably sweaty — part of summer.
Cooling systems
The human body comes well equipped with heat-loss mechanisms. As core temperatures rise, sweat glands pump water through the skin. Sweat evaporates, taking body heat with it.
Sweating’s not the only way we have to cool down. Higher body temperatures cause the heart to pump more blood to the skin. Skin blood vessels dilate, exporting more heat.
As anyone running in midday heat knows, these mechanisms can be severely impaired by weather.
As the difference between body temperature (98.6 degrees) and ambient temperature shrinks, heat moves less readily to the air.
When the mercury passes 100, we actually begin to absorb heat from the environment — that’s on top of the heat we’re absorbing directly from the sun.
Humidity adds an extra whammy. If the surrounding air is heavy with water, sweat cannot evaporate.
Size advantage
Other factors — such as body size — determine how hot we get. Studies have shown that lighter runners can run faster or farther before reaching exhausting core heats.
This doesn’t mean larger-framed athletes must exercise in the confines of a humidity-controlled, air-conditioned gym. Merely being fit helps too.
The stronger the cardiovascular system, said Glen Kenny of the University of Ottawa, the easier and more efficiently it pumps blood to the skin, where it can dump excess heat.
So if you can’t be small, be fit. While you’re at it, shed excess body fat, which strikes a double blow against heat tolerance. It adds more weight to move and insulates — like any clothing that’s bulky or doesn’t breathe — making it harder for heat to escape.
Be prepared
It’s hard to control all factors that play into overheating. Yet there are factors the athlete can more readily control. Among the most important: Take time to acclimate to the heat.
“Your body just does a lot of things to fine-tune itself to hot exercise,” said Douglas Casa, director of athletic training education at the University of Connecticut. People who regularly exercise in the heat have a lower resting body temperature, decreased heart rate and quicker and more generous sweating.
This doesn’t happen overnight. To prep for summer athletics, it takes 10 to 14 days of regular exercise in the heat, slowly building up to intense workout at the hottest times of the day. Most heat illness cases occur in people not used to working out in the heat, Casa said.
Stay hydrated
Sports physiologists also stress the importance of proper hydration. As water content drops, less is left for sweat — meaning less sweating and less cooling.
The American College of Sports Medicine recommends athletes ensure they are hydrated before exercise, keep hydrating during exercise and rehydrate afterward.
Because there is no formula that fits everyone, the ACSM suggests athletes try to replace fluid as it’s lost.
It also stresses that relying on thirst will not do the trick, because thirst kicks in only when 1 percent to 2 percent of body weight is lost.
Above that, many people find they aren’t really thirsty enough to fully replace fluids they sweat out — and, indeed, many studies report that athletes fail to do so.
A strategy for success? Casa suggests exercisers drink while working out and weigh themselves before and after: “If you weigh less, drink a little more. If you weigh more, you overdid it.”
Feeling the heat
Here’s what to do if you begin to feel overheated when exercising:
* Keep moving until you’ve cooled down. Stopping can cause blood to pool in the legs, leaving less blood to circulate to the brain, causing dizziness.
* Make sure your legs are elevated and moving if you’re experiencing extreme fatigue and must lie down. This will help maintain cardiac function and blood pressure.
* Head for a cool room or some shade if it’s a hot, sunny day. Use an ice pack, take a cool shower or bath, or plunge into the ocean or pool to cool core temperatures.
* Make sure you’re drinking enough water to fend off dehydration. [L.A. TIMES]
SET A ROUTINE
An ideal cardiovascular workout should consist of a warm-up, stretching, exercise and a cool-down. Each phase is important. Make sure to schedule all phases into your workout, shortening your cardio if necessary.
Warm-up
A few minutes of warm-up prepares the body for exercise, literally heating up the body’s inner temperature. Light cardio — such as slow jogging, walking, leisurely bicycling — raises the heart rate, pumping blood to the muscles.
Stretching
Do this after warm-up, because stretching cold, stiff muscles can cause injuries. Don’t force stretches. Do them gently, focusing on ones that will be used during exercise.
Cool-down
After your cardio, it’s important to allow the body to cool down, even if it wasn’t a particularly sweaty workout. This stage allows the body’s core temperature and heart rate to return to normal. Begin by slowing the tempo of your activity.
* If coming off a run, slow to a jog and then a walk.
* If swimming, continue at a more relaxed pace, or simply move around in the water.
* After running on a treadmill, it’s OK to hop over to a stationary bike and pedal slowly.
[L.A. TIMES]Drink cold during, warm after
Make sure whatever fluid you drink before and during exercise is icy cold.
A team led by David Jones of the University of Birmingham, England, had eight men cycle to exhaustion in 93-degree Fahrenheit heat. Those who drank cold fluids biked seven minutes longer than those given warm drinks. They also had slightly lower temperatures and heart rates, and drank 1.4 quarts of fluid compared with 1 quart of room-temperature water.
Paradoxically, after exercise, drinking cold water might be worse for hydration.
“It satiates you more, so you drink less,” co-author Toby Mundel said. That’s when you should drink something at room temperature. [L.A. TIMES]
