Staying Healthy While Exercising in the Summer Heat

Heat effects the human body in many ways, not the least of which is the effect on what your body needs to do to allow you to exercise in the summer heat. You may have heard of the list of heat-related illnesses that can be caused by exercising in the heat. They can range from heat cramps to the life-threatening heat stroke. Now is the time to review them and discuss their causes and symptoms, as well as treatments, so you can enjoy your summer exercise sessions while limiting the risks of heat-related illnesses.

Heat-related Symptoms and Illnesses

Under normal conditions, your skin, blood vessels and perspiration levels adjust to the heat to create your body’s natural cooling mechanism. To regulate your body temperature, heat gain or loss is controlled by the autonomic nervous system’s alteration of heat flow from the body’s core to the skin via surface blood-flow and sweating. During exercise, your body temperature initially raises to allow the muscles to optimally function (warm up) until heat production reaches an optimal level, then the bodies thermoregulatory system begins to expel heat until production of heat equals loss of heat via sweating and increased blood flow to the skin (Sawka).

The graphic below is an example of the heat forces being forced on the body during exercise and the body’s cooling responses pushing the heat off the body.

(McArdele, 503)

Despite this highly effective cooling mechanism, during exercise the muscular system requires an influx of blood to allow the activity to be performed. At this point, the muscles call for more blood, and in normal humans the needs of the muscle outweigh the needs of the skin, so the blood is rushed into the muscles. The body goes into a complicated interplay of cooling the skin via blood and movement created by blood vessels and their need for blood. The large amount of blood needed to perform all of these activities creates a cardiovascular strain which results from the reduction in cardiac output (less blood circulating from the heart to the body), skin and locomotor muscle blood flow decrease, and less oxygen being delivered to the skin and muscles which causes decreased ability to perform the exercise to its fullest potential and a decrease in the body’s cooling ability (Gonzalez-Alonso, 45-53).

This highly organized cooling mechanism is further stressed in the heat by the rapid onset of dehydration and hyperthermia (increased body temperature). If the body is not properly hydrated and cooled, your body will progress through the following stages of heat-illness:

  • Heat Cramps are painful cramps in the stomach, arm and leg muscles that are caused by not replacing salt and fluids during prolonged and/or intense exercise in the heat.

  • Treatment: Stop exercising, drink cool water or electrolyte solution, and gently stretch the affected muscle.

  • Heat Syncope is weakness, fatigue and fainting that are caused by too much salt and water loss through perspiration during exercise in the heat. This is normally caused during the first 5 days of adjusting to a new activity, and can be complicated by taking diuretic medications or a previous heat-related illness.