How hot is “too hot” for outdoor exercise?

Temperatures are rising all across the United States with little relief in sight. Most of us look forward to summer.  The longer daylight hours, the sunshine and warmer temperatures – perfect for getting outdoors to exercise.  But is it always?  As seasonal temperatures peak during this time of year, when is it too hot to exercise safely outdoors?

When we take our workouts outside in the high heat of summer, it can make you vulnerable to risks like heat exhaustion or heat stroke.  However, with some common sense and paying attention to the weather forecast, there is no reason why you need to avoid getting in a good workout in the great outdoors.  As long as you know the risks and know what your personal limits are, you should still be able to enjoy being physical in nature.

Here is what you need to know in order to exercise safely outdoors:

·      The World Health Organization recommends a maximum temperature of 75 degrees for “comfortable” exercise. 

·      Temperature may not necessarily be the biggest determining factor or concern – rather humidity is a greater threat as it affects your body’s ability to cool itself down.  When exercising in a dry heat, sweat will evaporate, but on a humid day, your sweat is more likely to remain on your skin without evaporating.  When sweat clings to your skin, it is harder for your body to maintain a safe temperature.

·      Do not push yourself in high heat and humidity.  Working out in very warm temperatures will cause your body to sweat a lot to cool itself.  When this happens, your blood rushes to the skin to cool it, which means there is less blood in your muscles.  That can make your blood pressure drop and your heart rate to increase, causing lightheadedness. 

·      Use the heat index for gauging if it is safe to exercise outdoors.  Heat index is what the temperature feels like to the human body when relative humidity is combined with air temperature.   While a 90 degree F outdoor temperature is relatively safe at 10% humidity, the heat stress of 90 degrees F at 50% humidity is the equivalent of 96 degrees F.  It is generally recommended that when the heat stress index hits 90 degrees, stay indoors in air-conditioning to work out or postpone your exercise session until later in the day. 

·      Pay attention to how you are feeling while exercising and know when to call it quits when you don’t feel well.  Recognize and pay attention to the symptoms of heat exhaustion and heat stroke and what to do  to prevent them from happening.

·      Avoid outdoor exercise during the hottest part of the day (11 am to 4 pm).

·      Keeping well-hydrated is very important - Prep for a hot weather workout by drinking about 16 to 20 ounces of water about an hour before you plan to head outdoors.  While working out, drink at least four ounces of water every 15 minutes. 

·      Always wear sunscreen and loose, light colored clothing.

By following the above suggestions of not pushing too hard, staying well-hydrated, know the signs of heat stroke or exhaustion, knowing when to stop, and remembering the saying, “It’s not the heat, it’s the humidity,” can save you from heat-related problems while still enjoying outdoor exercise this summer.