“There’s this entrenched idea that it’s good to ‘sweat things out,’” said Oliver Jay, an associate professor of exercise physiology and director of the Thermal Ergonomics Laboratory at the University of Ottawa in Canada, and by extension, that sweating heavily during exercise is somehow healthier than misting daintily. But in fact, “sweating, per se, provides no health benefits,” Dr. Jay said, apart from preventing overheating. The benefits derive from the exercise itself, and the more intense, generally, the greater the health benefits.
Core temperature rises during prolonged and vigorous physical activity, though, and your body must shed that heat. It does so in large part by sweating. The more vigorously you exert yourself, the more internal heat you produce, and the more you must sweat. Such strenuous exercise improves health through many different physiological mechanisms. But perspiring, in and of itself, does not provide or amplify those effects, Dr. Jay said.
That situation doesn’t change if you’re sweating due to a hot environment. “Sweat is sweat,” he said. You will perspire more if the air is humid, he said, because sweat doesn’t evaporate efficiently in humidity, and it’s evaporation that actually cools your body. But you aren’t gaining extra health benefits from drenching your clothing with perspiration; you’re only ensuring that you’ll need to sip from your water bottle more often to avoid losing too much fluid.
As a rule of thumb, drink when you feel thirsty, so that sweating doesn’t become actually unhealthy.