A recent study out of South Korea used chemicals to induce maximal sweating in long-distance runners and couch potatoes. They found that long-distance runners began sweating faster and sweat more per gland. This finding follows decades of research that says athletes sweat more than non-athletes. "Just like many other adaptations your body goes through when you train, [sweating] gets more efficient," says Janet Rankin, professor in Virginia Tech's department of Human Nutrition, Food, and Exercise. However, other research suggests that the elevated sweatiness of athletes may be mostly due to the fact that they are simply working out harder. So which is it?
In order to examine the sweat differences between the fit and unfit, researchers from the University of Ottowa studied 14 men, half with high aerobic fitness, half with low, and all with nearly the same body weights and skin surface areas. When these men worked out at the same relative intensities (60 percent of their maximum), the athletes sweat more. Yet when they worked out at the same absolute levels, regardless of personal ability, they sweat the same, which suggests that the athletes only sweat more because they exercised harder. Put this together with the other study and it looks like athletes generally sweat like everyone else but may sweat more if their sweat rate is pushed to its maximum (as it was with the chemicals).
This research is important because sweat plays a crucial role in our body, it can do a lot of good but is also potentially harmful. Our body releases sweat – mostly made of water and sodium – onto our skin in hopes that it will evaporate. If it evaporates, it takes some energy (heat) with it and cools us down. However, if it's too hot and sweat is just dripping off your skin, you lose out on that cooling effect. Sweat can also benefit us by opening our pores and warding off bacterial growth. Unfortunately, sweating a lot is not all that advantageous because it increases a person's risk for dehydration and mineral loss.
Fluid loss can be easily estimated by tracking your weight before and after working out. Rankin says that one kilogram of weight loss is equal to about one liter of fluid loss and that person should drink 1.5 times as much fluid as they've lost. Tracking mineral loss is not so easy. People are working on sensors that can monitor a person's sodium levels but, for now, Rankin says drinking fluids with electrolytes during any intense or hot weather workout is vital if you want to keep performing at your best.