A new study from her lab shows that a 20-minute moderate workout has measurable effects on the immune system: Participants were asked to walk or jog on a treadmill, depending on their fitness level. They measured levels of TNF, an inflammatory marker, before and after the exercise, and found that there was a 5% reduction in the number of immune cells that produced the marker.
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.