Summer heat can be deadly, especially for athletes. Prolonged exercise in hot weather greatly strains the cardiovascular system. In excessive heat, the body requires more blood flow in order to help the muscles sustain work and the skin and sweat glands to cool the body without compromising the precious blood supply to the vital organs. This puts a huge burden on the heart.
High humidity compounds the problem. The body vigorously attempts to maintain a normal core temperature of 98.6 degrees Fahrenheit and sweating is the one meaningful cooling mechanism to achieve this. However, sweat must evaporate to get any cooling effect. In high humidity, the air is already saturated with moisture, reducing the driving force for evaporating sweat. A relative humidity above 70% can render the sweat response largely ineffective and result in wasteful loss of body fluid.
The combination of heat and humidity creates conditions that increase the risk of developing heat-related illness such as heat exhaustion or heat stroke. Safely navigate your summer training by sticking to these rules for exercising in hot and humid weather:
- Acclimate yourself to the heat. Although no one is immune to the heat, the single best defense in preventing heat-related illness is acclimatization. Your body adapts to the heat by increasing blood volume and sweating earlier and in greater amounts. Generally, it takes a week or two to fully acclimate, so start slowly when training in the heat.
- Have a strategy to stay hydrated. You can lose up to two liters of fluid per hour during exercise. When lost fluid is not completely replaced, you may become chronically dehydrated. Drink liberally in the evenings after your workout. Sports drinks can be helpful in replacing electrolytes. The goal is to drink enough to get back to a baseline weight before the next training session.
- Take proper precautions. Avoid exercise in the heat of the day by planning your workout for the morning or late evening. Wear loose-fitting clothing with wicking properties to allow for ample evaporation of sweat.
- Be aware of the symptoms. Signs of heat exhaustion can begin suddenly and resemble the onset of shock. You feel weak, dizzy, light-headed or worried. You may also have a headache, fast heartbeat or nausea. If you don’t rest or cool down immediately, this can quickly develop into heat stroke. If these symptoms do not abate or you feel confused or have difficulty walking, see a medical professional immediately, as this is a state of medical emergency.