A Chilling Effect

By Ed Eyestone

Runner's World-January 2008

With this weekend's return to Daylight Savings Time, the promise of spring and warmer weather seems to be closer. Spring can also mean a lot of temperature fluctuations, (especially here in Reno) and if you do any kind of outdoor training, such as cycling, running or walking, you might find it interesting to know how the outdoor temperature can affect your performance. Last month's Runner's World ran an article on this subject by Ed Eyestone, coach of the men's cross country team at Brigham Young University. While this article, "A Chilling Effect" is geared primarily to those who are trying to improve their performance in races, it is interesting for anyone who likes to exercise outdoors.

Eyestone explains in the article that if you are exercising outdoors in cold temperatures your core body temperature will often fall below 98.6°, " which means that your body will require 15 to 20 percent more oxygen to maintain the same pace." This results in the heart pumping less blood, so obviously, it will take you more time and effort to complete your workout.

While most studies show that runners perform better at 36°F than at 70°F, there are individual variations. And, your level of acclimitization is a big factor. Simply put, if you have been training in cold weather for a considerable length of time, you will be able to perform better in lower temps. This is because repeated exposure to colder weather seems to increase blood flow, which results in higher skin temperatures. But more than the physical changes, the psychological edge that one can gain through training in adverse weather can make a sizable difference! (The same obviously holds true for those training in hot weather.)

The article contains an inset titled "Pray for 50°" and includes the following text: "If endurance runners could control the weather, it would always be between 36°F and 52°F. One study reported that athletes exercising in 36°F temperatures took 30 percent longer to reach fatigue than those exercising in 68°F, and 65 percent longer than those in 104°F heat. Another study suggested that 52°F was optimal. Here's an example of how changes in temperature affectr a 44-minute 10-K runner.