Heat stress occurs when high humidity, radiant heat from the sun and elevated air temperature combine to impede your body’s ability to dissipate heat. It also places considerable demands on your body’s physiological control mechanisms.
To train and compete at your best all summer, it is important to understand how your body copes with heat, and what you can do to keep cool.
Eliminating Heat From Your Body
Your skeletal muscles can use only about 25 percent of the energy available to them to generate force; the other 75 percent of energy is released as heat during prolonged cycling, heat production can potentially raise your body temperature nearly 2 degrees Fahrenheit every five to eight minutes.
If the body did not adjust to this condition, exercise would be limited to about 20 minutes before elevated body temperature caused fatigue.
But exercise can be sustained for longer than 20 minutes, so your body must possess some mechanism to dissipate heat. In fact, there are four ways that excess heat produced by muscle contraction can be removed from the body: conduction, convection, radiation and evaporation.
Excessive heat strain during exercise usually does not occur unless temperature and humidity are high, the air is stagnant, you do not rehydrate effectively, or you are not adequately acclimatized to the heat all of which happen during the summer months.
However, when cycling, the wind moving across your body can usually remove the heat produced. This is convective heat lost, and is related directly to wind speed.
Sweating is important to help regulate body temperature during hard training. As sweat evaporates, heat is removed from your body. However, humidity impairs this cooling mechanism, since air is already saturated with water and sweat doesn’t evaporate as easily.