Banner Health Services  

Running in the summertime heat

Dr. Bhow  

Moneesh Bhow, MD, is an emergency medicine physician on staff at Banner – University Medical Center Phoenix.

Question: I recently began training for a half marathon and want to continue running during the summer, but I worry about the heat. Is it safe to continue exercising outside? 

Answer: Heat-related illnesses cover a broad spectrum that can range from muscle cramps to heat stroke. Heat exhaustion, which falls within this spectrum, is usually a result of dehydration coupled with an elevation in body temperature that is often brought about by exertion in high external temperatures. When running or performing other physical activities in hot and/or humid weather, it is paramount to stay hydrated and heed the warning signs of heat-related illness. 

When the body is not properly hydrated and internal temperatures rise, muscle cramps and/or spasms can occur. If not treated at onset, symptoms can progress and, ultimately, lead to heat exhaustion, which is characterized by dizziness, lightheadedness, headache, increased heart rate, sweating and even passing out. Further progression of these symptoms can result in a life-threatening heat stroke. 

Heat stroke shares many of the signs and symptoms of heat exhaustion; however, heat stroke is generally accompanied by noticeable changes in mental state and no longer sweating despite being very hot. These dangerous signs highlight extreme dehydration and constitute a true medical emergency.     

While resting in a cool environment and drinking fluids is usually enough to treat mild symptoms of heat illness, severe cramping and symptoms of heat exhaustion require salt-containing fluids to help replenish electrolytes. A combination of sodium and potassium, electrolytes are essential to proper cellular function. Sweat, which is high in sodium, is the primary channel through which electrolytes are lost. Rehydrating with water alone cannot restore depleted sodium and potassium levels and may lead to an electrolyte imbalance. Commercially available beverages like Gatorade or even salt tablets that are dissolved in water can help keep electrolyte levels in check. 

As is often the case, prevention is the best medicine for heat-related illnesses. When temperatures are high, decrease your outdoor physical activity, reschedule workouts to cooler parts of the day, wear light/loose-fitting clothing, drink plenty of fluids, avoid alcohol and carbonated beverages, and keep electrolyte-replenishing drinks handy.

Heat-related illnesses spike in May and June since people often do not recognize that summer and the accompanying heat dangers are upon us. While the elderly and very young are most vulnerable to heat-related illnesses, everyone should be aware of the potential dangers associated with outdoor training and activity during the summer.

Page Last Modified: 02/27/2015
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