It zaps anxiety. Ever notice that you can start a workout feeling stressed and anxious, and end it feeling good? It isn't in your head. Or, actually, it is: According to a new study from Princeton University, exercise appears to change the chemistry of the brain by causing the release of GABA, a neurotransmitter that helps quiet brain activity and minimize anxiety. The study found that people who ran regularly had a low reaction to stressful situations, even if they hadn't run in more than 24 hours.
Here's some quick physics fun: A body at rest tends to stay at rest. That's the fitness version of Newton's First Law, and it means that humans will find literally any excuse to not work out. I don't have time.... I felt a slight ache in my knee and don't want to make that worse... It's high tide. Somewhere. Probably. This happens to everyone—even the most dedicated, ruthless, disciplined gym-goers among us. (Like we said, it's science)
The skin also serves as a release point for heat. (See “Why Does My Face Turn Red When I Exercise?” for more on that.) When you exercise, your muscles generate a lot of heat, which you have to give up to the environment so your body temperature doesn’t get too high, Hackney says. The heat in the muscle transfers to the blood, which shuttles it to the skin; it can then escape into the atmosphere.