Like a lot of people, I exercise to keep myself healthy and because it makes me feel physically better and mentally less stressed. I’m a competitive triathlete, and I prefer to do my training outside. However, working out in the heat has its challenges.
This morning, for example, I decided to do a medium length run (10K) in the morning before it got too hot. It was only about 85 degrees, so I got myself hydrated and stretched and started at a moderate pace. After about 4 miles, though, I noticed an odd sensation – my arms and legs felt cold, and despite the heat and sun I felt a chill. I saw goosebumps on my arm, which felt cold and clammy (well, as cold as can be under the circumstances).
I have a race next month, and I really wanted to finish my run, but this was concerning. I dropped to a walk and considered. It was clear that something was wrong – sweat is our primary way to keep cool, but the blood supply to my skin was not what it needed to be to exchange the heat. Without the ability to lose heat through sweat, the increased muscle work and heat, sun, and humidity would conspire to raise my body temperature. That does bad things to muscles and stresses the whole system. In severe cases, the syndrome is called hypovolemic shock, and this shuts down the blood supply not only to the skin, but to the kidneys, gut and liver as well. Although the body usually recovers, it’s pretty clear that the risk of continuing to exercise under excessive heat stress outweighs any benefit you might be getting.
By the time I got home, I was feeling fine, my skin was back to normal, and I was sweating appropriately, so I knew I wasn’t in any danger. In the emergency room, when we really want to cool someone down quickly, we use a fan – we don’t pack them in ice cubes. Cold air, and especially ice or cold water, constricts the blood vessels in the skin and doesn’t allow for the most heat transfer. Keeping someone wet with tepid water and under a fan maximizes the body’s own system for keeping cool. A lukewarm shower and fan works well too.
So, if you are like me and incompletely adapted to exercise in hot weather, you should listen to your body. Feeling cold and goosebumps is a sign you are overheating. You should immediately walk, hydrate and cool down. You can always finish your workout another time or switch things up by taking a refreshing swim. If you notice that this happens often, seek the advice of your doctor.