Exercising When It's Hot Outside

Jeffrey Heit Health Guide

    Have you looked at your calendar recently? We're heading into what are called the "dog days" of summer. Temperatures are at their hottest and humidity levels can be oppressive. It is therefore important to understand what effect this weather may have on your outdoor workouts, and what measures you can take to avoid dehydration, overheating and heat stroke.


    When the temperature soars, your body needs to do more to cool itself off and maintain a normal body temperature range. Usually, this involves dilatation of the blood vessels that are closest to the surface hence allowing heat to dissipate through the skin. Also, sweat glands work overtime to create a layer of moisture on the skin, helping to promote heat loss.

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    If, for instance, you jog one hot summer afternoon, your body needs to work double time- firstly to do the exercise itself, and secondly, to help keep your body cool. Your heart will pump harder and faster not only to supply your legs and arms with blood, but also to keep adequate blood flowing through those dilated blood vessels near the skin. Heat and humidity create less of a gradient down which body heat can be whisked away.
    As you continue to produce sweat and breathe faster, significant amounts of body fluids are lost and dehydration can occur. Moreover, electrolyte imbalances can often follow and be very serious.


    Some simple tips and common sense are important in keeping your workouts safe and injury free during the summer months.


    1. If you are going to exercise outdoors, try to do it either very early in the morning or later in the evening after the sun has set. Often, temperatures may be 10-15 degrees cooler at those times.


    2. Wear loose fitting, lightly colored clothing that reflects the sun's heat and are made of materials that are designed to keep sweat away from the skin. A good running or biking store will usually have a nice selection to choose from.


    3. Stay well hydrated! I cannot overemphasize the importance of this one. Drinking plenty of water as well as sports drinks will help keep you hydrated. Be careful though. Losing a lot of fluid through sweat and replacing it only with plain water can essentially dilute sodium levels in the blood leading to a condition known as hyponatremia. This condition can be serious and may lead to convulsions or even death. A combination of water and sports drinks is probably the best way to go. Sports drinks such as Gatorade and Powerade replenish much needed sodium and potassium; plain water does not. Carrying some foods that contain salt and potassium may also be helpful such as pretzels and bananas respectively.


    4. Know the signs and symptoms of heat stroke and dehydration. Dizziness, lightheadedness, nausea, confusion, vomiting, flushing, and disappearance of sweating can all be early signs of overheating. Should any of those occur, immediately stop what you're doing, get into shade or indoors and continue to drink fluids.


    If you are going to exercise outdoors, it may not be a bad idea to workout with a partner so both of you can keep an eye on each other. On days when the National Weather Service issues excessive heat warnings where the "heat index" (a number that takes into account the heat and humidity) is 100º or higher you may be better off not exercising outside at all. If you belong to a gym, it may be a good time to take advantage of your membership. Working out is important but should not overshadow common sense. If you think it may be too hot to workout, trust your instincts and skip a day or two. Of course, you are always encouraged to speak to your primary care provider regarding specific concerns about exercising during the hot summer months.

Published On: August 06, 2008