Let me introduce you to your good friend, sweat. Ignore the gross feel and the potential for B.O. for the moment, and think about what it does for you: When your body gets too hot, threatening to raise your core temperature over what’s healthy, little glands in your skin squeeze drops of moisture onto its surface. As soon as a breeze hits those droplets, they evaporate, taking some of your body heat away with them.
This is true even during exercise. It’s not the exercise that makes you sweat; exercise just raises your body heat, and it’s the heat that makes you sweat. That’s why you sweat without exercising on a hot day, and why you can sometimes exercise without sweating in a cold environment. In other words, sweat means a lot less than you might think. Sweating doesn’t mean you’re getting a good workout, doesn’t mean you’re losing weight,
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