KEEPING COOL: Let Them See You Sweat. “Don’t wipe unless you’re drenched. Sweat releases heat by evaporative cooling. As each gram of sweat transitions from liquid to gas phase, it absorbs 2,427 joules of energy from the body and dissipates the heat into the environment. But if you wipe away the perspiration before it evaporates, that process will get cut short, and you’ll need to sweat more just to achieve the same degree of cooling. On the other hand, any sweat that drips to the ground before it can evaporate won’t do you any good, so if you’re really soaked you may as well reach for the towel.”