How much are you supposed to sweat during a workout? Could excessive sweating be a sign of something serious? Dr. John Clothier, a family and sports medicine physician with Dignity Health Medical Group in San Francisco, talks about sweat and what's normal for those who workout in this Q&A.
How does sweating work to cool the body?
Sweating is an adaptive feature of mammals to eliminate heat and humans may be the most adapted. Heat is created by the body when we participate in physical activities, and at the same time energy is consumed. A majority of the energy consumed while exercising is converted to heat, as much as 75%, and a significant minority is translated in the form of muscular motion while we workout.
Why is sweating important for your health?
Our bodies need to maintain a certain temperature to function optimally, so when excess heat is created during exercise, it must be dissipated. Sweating and the evaporative cooling effect it causes is our best resource for maintaining the right body temperature when we get hot. As we sweat, the water on our skin absorbs the heat from the skin. When sweat is converted to water vapor it physically removes heat from the body.
Why do some people sweat more than others?
It may be hard to believe, but we are born with a set number of sweat glands. And this number is determined by the time we are 2-3 years of age. What can change as we get older, taller, and larger is the density of the sweat glands per unit area of skin. This means larger individuals have fewer sweat glands per unit area than their leaner counterparts, which puts them at a cooling disadvantage.
Remember that the body is amazing at adapting. If you start training and running, your body may increase the size and number of superficial veins to monopolize on the cooling effect of sweat. This process has a similar cooling effect as an automobile radiator. So if you sweat a lot, think of it this way: your body is a doing a great job of trying to cool you off.
Are there downsides to sweating too much?
Obviously in certain circumstances, sweating a lot can be seen as a bad thing. But for the most part, this is just a sign that your body temperature needs cooling. The rate at which individuals sweat is somewhat variable, and the amount you sweat mostly relies on how much each of your sweat glands can produce, rather than the total number of sweat glands your body has.
The average sweat rate for an aerobic activity under moderate intensity is 2L/hour. The content of sweat is mostly water with some other elements including sodium, potassium, calcium, and magnesium. (Other solutes in sweat include; zinc, copper, iron, chromium, nickel and lead.) So if you sweat a lot, you’ll really want to make sure your replenishing your fluids and nutrients!
Anything else you’d like to add?
If you’re training or working on becoming athletically fit, your body will eventually adapt to the training effect. Rigorous training results in better cooling effects and less salt lost per unit volume of sweat. It also results in a more efficient ability to channel cooling directly to the superficial veins.
Always remember to drink water and take in some salt on that next run!