You’ve probably experienced the sensation of running around for the first time in the scorching summer weather. The legs are fine for awhile, but soon they feel like they are sloshing through thick, sticky molasses.
And as the unrelenting heat continues to smother you, the sweat seems to roll effortlessly off your skin, your lungs are increasingly impotent as they try and absorb every molecule of oxygen from the air and your muscles get shaky and loose coordination as your energy supply starts to dwindle.
As we have emerged from our cool cocoon of spring and very suddenly launched headlong into the full throes of summer, we must be aware of the effect that heat has on exercise and also know what to expect as the body acclimates to the heat. That way we can stay safe and make the most of our exercise and outdoor play.
The gradual build up of heat in the body is called heat stress and is a great concern for exercisers during play in the summer months. By slowly allowing the body to adapt to higher temperatures, we can prevent heat cramps, heat exhaustion, heat stroke, and life threatening hyperthermia – this process is called acclimatization.
The average person has more than two million sweat glands. Sweat is made up of water and electrolytes, such as sodium, chloride, and potassium. When the core temperature of the body increases, the hypothalamus increases blood flow to the skin, which stimulates the sweat glands. The result is an increase in the rate of water and heat loss through sweating.
The reason why we feel tired much sooner in the heat is that as our bodies send more blood to the skin for cooling, this draws much needed blood away from working muscles and causes a lower amount of blood available to the heart leading to higher heart rates at any given work load.
The loss of electrolytes and fluid from sweating will lead to a decreased blood volume and add additional demand on the entire circulatory system.
All these organs and systems will change and adapt to heat stress, given enough exposure.
Heat acclimation is the process whereby an individual is able to maintain a higher blood plasma and volume level, increased sweat rate, a reduction of salt in the sweat, a reduction in the fatigue rate of sweat glands, and quicker response of sweating when heat stress occurs.
Acclimation is produced from repeated exposure to heat sufficient to raise body core temperature. It will occur more quickly and effectively by exercising instead of sitting in a hot room or standing in the sun for example.
Only a few sessions of one hour of moderate exercise in the heat will produce physical changes in un-acclimated individuals in as little as a few days to about one week. However, the feeling of normal exercise ability (perceived exertion) in a hot environment can take up to one month to occur.
The bottom line is, go out and enjoy the sun, using proper sunscreen and fluid replacement, but be patient, and take it in smaller doses initially, gradually increasing your exposure time.
If you are an athlete in training, be wary of the signs of heat stress and adjust your training intensity and duration accordingly.
Kerry Senchyna holds a bachelor of science degree in kinesiology and is owner of West Coast Kinesiology.
