RPE or Rate of Perceived Exertion is a scale used to measure the intensity of your exercise. The RPE scale runs from 0-10, with the numbers on the scale ranging from easy to very difficult. Generally in 55 degree weather, our bodies will adapt to the environment by perspiring to cool the body down and in a less humid environment, the excess perspiration will evaporate more quickly than in the higher humidity. Our RPE in this environment when running or exercising at a moderate pace may be a 4 or 5. This can dramatically change when the temperature and humidity increase. When the weather is between 60 and 75 degrees, heart rate can increase by 2 to 4 beats per minute. In 75 to 90 degrees, heart rate increases by 10 beats per minute with humidity amplifying these effects even more. In turn, one’s RPE in 55 degrees can dramatically increase with the same type of exercise in 75 to 90 degree weather.
In addition to sweating and fluid loss in the heat and humidity, blood volume will decrease, meaning less oxygen-rich blood is returned to the heart and less blood is shuttled to the muscles. As we get hotter, the greater amount of heat that is needed to dissipate will require a higher portion of the blood to go to the skin to cool us off.
So before stepping outside to take that run or do a trail, consider your current RPE, always remember to hydrate and adjust your mindset to adapt to the changing environment. Stay safe and move with purpose.
Training in the Heat. (2016, February 02). Retrieved July 11, 2017, from http://www.runnersworld.com/race-training/training-in-the-heat?internal_recirc=outbrain_af
Perceived Exertion (Borg Rating of Perceived Exertion Scale). (2015, August 11). Retrieved July 11, 2017, from https://www.cdc.gov/physicalactivity/basics/measuring/exertion.htm