Jumping on the treadmill or cross trainer for 30 minutes can blow off tension by increasing levels of "soothing" brain chemicals like serotonin, dopamine, and norepinephrine. What's fascinating, though, is that exercise may actually work on a cellular level to reverse stress's toll on our aging process, according to a 2010 study from the University of California—San Francisco. The researchers found that stressed-out women who exercised vigorously for an average of 45 minutes over a three-day period had cells that showed fewer signs of aging compared to women who were stressed and inactive. Working out also helps keep us from ruminating "by altering blood flow to those areas in the brain involved in triggering us to relive these stressful thoughts again and again," says study coauthor Elissa Epel, an associate professor of psychiatry at UCSF.
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.