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.
Previous studies from her lab have also shown that the exercise is linked to changes in the secretion of stress hormones like epinephrine (a.k.a. adrenaline) and norepinephrine. “Our work has shown that each moderate, relatively short exercise bout exerts regulatory/suppression effects over inflammatory activities of immune cells," says Hong, "and in order to maximize this ‘benefit,’ repeated and regular exercise is recommended. In fact, we have also found that higher physical fitness is associated with better regulation of inflammatory activities of immune cells through stress hormones even among obese individuals.”
Exercise has long been correlated with a longer life, but it’s only recently started to become clear why this might be. Studies, like a new one in the journal Preventive Medicine which found that exercise is linked to longer caps at the ends of chromosomes, have helped flesh this out a bit more. These caps, called telomeres, naturally shorten as we age, with each cell division. People who live a long time have telomeres that are in better shape than those who don’t—but there’s a lot we can do to affect the rate at which they shorten over the years. The team behind the new study looked at data from CDC's National Health and Nutrition Examination Survey, and found that for people who exercised regularly, their telomeres were 140 base pairs longer on average than sedentary people's. Which correlates to being years “younger” than their sedentary peers.