The effect of heat on exercise

Heat: Everyone knows that when there’s too much of it, things can get very uncomfortable, especially if there’s an accompanying high humidity. However, a high temperature is also something that needs to be considered if you are training under these conditions. Besides the general notions to drink plenty of fluids and stay hydrated, excessive temperatures can also adversely affect your performance, so any benchmarks or goals you set for yourself need to be adjusted depending on the conditions.

Take, for example, the route that I have been running for the past several weeks. During that time, I’ve kept records of my run times along with the conditions that day. (Specifically, the temperature, dew point and relative humidity)

On days where the temperature was above 25C my run times were averaging between 45-46 minutes. On days where the temperature was 20C or lower, average times decreased to around 43 minutes. That’s roughly a 4-6% decrease in time when going from 25C to 20C, or conversely, a 4-7% increase in times when going from 20C or below to 25C or higher.