Are you training in the heat? Read this article for some great tips on how to do it safely.

Many runners are going out for their morning runs, even in our 100+ heat we suffered through last week. While it is important to stay properly hydrated, running in high humidity with high ozone levels can be dangerous and make you feel winded and out of energy, even if you are in an air conditioned building.

Running Times magazine offers some sound advice for those who want to go out when it is hot.

Training in the Heat

Why you’re slower in the summer and what to do about it

By Kristin Barry Published July 19, 2011

As year-round runners facing myriad conditions, we all recognize that it’s harder to run well when it’s hot. Perceived effort is greater and race times typically suffer accordingly. Why does this happen? What happens to the body at a physiological level? And most important, how should we adjust workouts and race expectations to best weather the weather?

It’s generally recognized that for every 10-degree increase in air temperature above 55 degrees, there’s a 1.5 percent to 3 percent increase in average finishing time for a marathon. (Translation: An extra 3 to 6 minutes for a 3:30 marathon with every 10-degree increase.) This slow-down occurs because heat impacts runners at a physiological level through various means, including dehydration, increased heart rate and reduced blood flow (and subsequently oxygen) to the muscles used for running.

SWEAT: THE DETAILS

Thermoregulation is how your body maintains a consistent internal temperature. When exposed to external heat, your body cools itself and maintains equilibrium via perspiration. Perspiration has a cooling effect on the body because it removes excess heat through evaporation. The rate of evaporation–and subsequently how well the body is cooled–changes depending upon humidity. When humidity is low, evaporation increases; when humidity is high, the rate of evaporation decreases and less cooling occurs.
Sweating, while critical to cooling the body, leads to fluid loss. Dehydration from fluid loss has a profound effect on running performance–a loss of even 2 percent of body weight leads to about a 4-to 6-percent drop in performance. Furthermore, both temperature and humidity increase heart rate and amplify these effects. At 60 to 75 degrees, heart rate increases by two to four beats per minute. From 75 to 90 degrees, heart rate increases up to 10 beats per minute, and humidity increases it even more. Perceived effort is accordingly much greater as both the temperature and the humidity rise.