desert heat exercise post

Heat illness can be deadly. We have witnessed that with the recent spate of tragedies in the wake of Phoenix’s near-record heat wave last weekend, including hikers who died in the hills just behind our house in Paradise Valley. It is a stark reminder of the real danger of overheating.

Despite the oppressive heat, the mountains still call. I admit, I am addicted to exercise and cannot bear the thought of confining my workout to the treadmill or local gym. Trail running allows me to pass the time enjoying the cactus in bloom, the desert sunrise, the parade of hot air balloons rising over distant hills, and many varieties of birds.

How does heat affect the body?

Some people, even professional athletes, are more susceptible to heat illness than others for a number of reasons not yet fully understood by scientists. It is well known that the body can adapt to exercising in the heat over a period of days to weeks with regular exposure. A sudden change of climate without an adequate adjustment period invites disaster.

Know the physiologic limits of the body’s cooling ability. When core body temperature rises, blood vessels near the skin dilate to radiate heat to the skin surface, causing the skin to become flushed (red). This requires additional blood, leaving less for the muscles and requiring the heart to beat faster. The added stress requires even more energy, producing more heat. Evaporative cooling of sweat from the skin and of moisture from the airway and lungs helps release additional heat. Humidity in the air slows evaporation and reduces cooling ability.

How do you keep your cool while getting your workout on?

  1. Avoid temperatures over 90 degrees. This is a must. If you can’t get up early enough, use the gym instead.
  2. Avoid direct sunlight. Stay on the shady side of a mountain or in a deep valley with a shaded pathway. Many Phoenix road-biking groups start their morning rides at 5 a.m. or earlier during the summer, just as the twilight affords enough light to ride. Some recommend high-intensity exercise such as running only be done between 4 a.m. and 6 a.m. Evening hours help avoid the sun but the heat lingers well into the Arizona night.
  3. Maximize evaporative cooling. Wear loose, breathable, moisture-wicking, light-colored clothing. Maximize air movement by avoiding steep hill-climbing and using a fan when inside.
  4. Drink water. Even if you aren’t thirsty, keep drinking throughout and after. If you are unsure of how much to drink, you can weigh yourself naked (and dry) just before and after a workout, then replace the amount of weight lost in ounces. Try to keep your water ice-cold by using plenty of ice and insulating water bottles. If you’re serious about exercising in the heat, invest in the necessary hydration gear to allow you to carry water comfortably over long distances.
  5. Replenish electrolytes. Sweat carries salts from your body. Some lose more than others. If you drink large amounts of plain water without supplemental electrolytes from food or mixed into the beverage, you can dilute your blood to a dangerously low level and even cause the brain to swell.
  6. Do not pre-hydrate excessively if planning a long period of exercise such as a triathlon or marathon. It’s okay to drink a couple cups of water just before exercising but you shouldn’t drink excessively for days before a big event. This flushes your kidneys and reduces their concentrating ability, requiring you to urinate – and hydrate – more than necessary.
  7. Slow down. Adjust your peak performance goals. The ideal temperature is about 50-55 degrees for running. If you normally run a 9-minute mile at 50 degrees, expect to run a 10:30 or 11-minute mile at 85 degrees. At 100 degrees? You shouldn’t be running.
  8. Get cool before. I put my head into the sink and thoroughly wet my hair before a run in 80-plus degrees, and sometimes throw my shirt into the sink as well. Other rituals may also help such as the pre-workout slushy or ice bath.
  9. Get cool after. Use fans, cold damp cloths, shade, and ice water. When I come to a stop after a tempo run and the air movement stops, I find that my body temperature peaks and I sweat excessively. I immediately turn a fan on at full speed while stretching and drinking ice-cold water, and then I take a cold shower.
  10. Recognize heat illness. You may just feel unusually tired or strange at first. Then you may experience nausea/vomiting, weakness, muscle cramps, headache, and incoherence. Slow down, seek out shade, and drink and/or bathe in ice water if necessary. Athletes’ skin usually appears pale and clammy while those not exercising may have red, hot, dry skin. When core temperature goes above 105 degrees, the body’s organs begin to shut down. You don’t want to know what comes next. Carry a cell-phone and exercise in groups when possible.
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