Keeping Fit: Take care when exercising in hot weather
When the weather turns hot and humid, there are certain precautions that you should take to avoid exercise-related heat illness, such as heat exhaustion and heat stroke (which is often fatal).
Let’s begin by identifying the four means through which the body dissipates heat when you are not performing physical activity.
First, your body loses heat through radiation, meaning that you actually radiate heat from your skin into the surrounding atmosphere.
Second, your body eliminates heat through convection, such as the movement of air across your skin when the wind blows.
Third, your body transfers heat to cooler objects through conduction, which may be accomplished by touching your skin with a cold washcloth.
Fourth, your body cools itself by the evaporation of perspiration from your skin.
Your sweat glands send water to the surface of your skin, which uses body heat to change the water from liquid to gas.
This is a highly effective and efficient means for heat dissipation, and it is essentially the only avenue for cooling the body during vigorous physical activity.
Keep in mind that there are two essential steps involved in heat loss through sweating.
First, you must perspire at an appropriate level. Second, the perspiration must evaporate to provide a cooling effect.
To produce sufficient sweat, you must first be well-hydrated. Water is the best hydration fluid for short to moderate duration activity sessions, so be sure to drink water before and during your exercise period.
Also, replenish the lost fluids by consuming water after your workout. For long duration training sessions, you may prefer beverages that contain electrolytes and carbohydrates such as juices or commercial sports drinks.
While producing perspiration is the first step for body cooling, enabling the perspiration to evaporate from the skin surface is equally important. If the sweat stays on your skin, there is no real cooling effect. That is why you should wear minimal, light colored, light weight, and porous clothing for hot weather exercise.
Never use rubberized or plastic athletic attire as this type of clothing prohibits evaporation of perspiration and therefore prevents body cooling. Although the sweat accumulates on your skin it cannot change to a gas and thereby reduce your body temperature, making overheating a serious possibility.
Even wearing a regular sweatshirt when you definitely do not need extra clothing is a risky proposition. You will definitely produce more perspiration in your body’s attempt to cool itself, but most of the sweat stays trapped in the material, which significantly reduces evaporative cooling.
In addition to dressing light, try to avoid exercising during the hottest hours of the day. I recommend training in the morning or evening if possible. If you are a runner, attempt to use shaded trails whenever you can. Grass and dirt surfaces are much cooler than asphalt roadways or sidewalks (and also much less stressful with respect to landing forces and shock absorption).
Running on sandy beaches offers advantages with respect to soft surface and ocean breezes. Just be sure to run on the flattest section of the beach, as running on an angle places uneven stress on your feet, knees and hips.
On really hot and humid days, you may prefer cycling over running due to the greater air movement experienced at the faster cycling speeds.
Another alternative is water-based activities such as canoeing, kayaking, rowing and swimming. Temperatures are typically lower on the water, and ocean breezes are cooler than land breezes. Of course, exercising in the water is the best means for avoiding overheating, and swimming should be a preferred physical activity when the temperature and humidity are exceptionally high.
If hot and humid weather is accompanied by poor air quality, it may be best to exercise indoors. YMCAs and fitness centers offer air conditioned exercise facilities that are conducive to summertime training. If you prefer to exercise at home, I advise placing you indoor cycle, stepper, rower or treadmill in the cooler part of your house. This may be an air-conditioned den or the basement in front of a large fan.
The cooler your exercise environment, the better the training effect as you will be capable of working at a higher intensity and for a longer duration. Accumulation of body heat always attenuates physical performance, making your exercise session less productive and less pleasant. Therefore, make every effort to reduce heat accumulation and dehydration for safe and effective summer exercise sessions.
Wayne L. Westcott, Ph.D., teaches exercise science at Quincy (Massachusetts) College and consults for the South Shore YMCA. He has written 26 books on physical fitness and strength training.