Exercise and conditioning in the summer months – how to stay cool

By: Laura Wenger, PT, DPT, OCS

As important as it is to get outside and exercise on a regular basis, this can prove challenging in the heat of the summer; especially if you are unable to get out in the early morning or late evenings when the temperatures are cooler. There has been a lot of buzz in recent years about sodium supplementation and its effects on replacing minerals lost in sweat during workouts, but one topic that has been less clear is how sodium supplementation affects thermoregulation. 1 Thermoregulation is your body’s ability to maintain its core internal temperature.2 When exercising in hotter weather, not only does your body have to work harder to keep up with the activity level that you are participating in, but it has to work hard to regulate your body temperature so that you don’t overheat. Sweating is one of our body’s natural processes to help with regulating our temperature during exercise.1

A recent study sought to further investigate the effects of sodium supplementation on thermoregulation in trained endurance athletes.1 During each hour of exercise, endurance athletes typically sweat 1 to 1.5 liters of fluid, of which an average of 0.8 grams per liter is sodium.1  Some past studies have shown conflicting results as to whether or not pre-exercise sodium supplementation affected the rate of sweat loss or rise of core body temperature, so the authors of this study decided to take a new twist to determine how during-exercise supplementation affected these body processes.1  Specifically, the researchers hypothesized that the sodium supplementation would decrease the rate of sweat loss leading to adverse effects of increased perceived heat stress and increased time to exhaustion.1

In this smaller study, 11 endurance runners and cyclists put each athlete through two tests: One where they were given a placebo tablet to use during exercise, and the other where they were given a sodium supplementation capsule.1  These capsules, given to the athletes immediately prior to and at intervals throughout their workout, contained an amount intended to replace about half of the sodium lost during an average two-hour workout.1   The athletes were also give a certain amount of water to ingest during the workout to ensure that they stayed adequately hydrated.1  Before, during and after two hours of their respective exercise, the runners and cyclists were put through a series of tests in order to study their sweat rate, heart rate changes, thermal sensation (how warm they felt), perceived exertion (how hard they felt they were working), and their time to exhaustion with a time-trial test at the end of 2 hours of sustained exercise.1

And what did these researchers find? Sweat rate, skin temperature, thermal sensation, rate of perceived exertion, heart rate, and time to exhaustion were no different between the placebo and sodium capsule trials.1 Although this was a smaller study consisting of only 11 athletes and more research in this subject is warranted, the results of this study suggest that there may not be any clear benefit to loading up on sodium supplements during your summer activities in order to regulate your body temperature more effectively.1  However, what is clear is that regardless of your favorite summer activities, proper hydration plays an important role in thermoregulation.1  So don’t forget your water when you are out playing and enjoying these hot days!

  1. Earhart EL, Weiss EP, Rahman R, Kelly PV. Effects of Oral Sodium Supplementation on Indices of Thermoregulation in Trained, Endurance Athletes. Journal of Sports Science and Medicine. 2015;14: 172-178
  2. Holland, K. Thermoregulation. Healthline. 4 June 2013. Available at http://www.healthline.com/health/thermoregulation#Overview1 , Accessed 17 July 2015.