Regular exercise doesn’t weaken immune system
A study in the Journal of Sports Science and Medicine found marathon runners and elite athletes reported fewer annual sick days ...
As many Americans spend more time working out while staying closer to home and social distancing, an advertisement warns that exercise could put them at risk. The wisdomtolive.com ad sports the headline “Exercise Can Suppress Your Immune System.” “Did you know that every time you perform an exhausting workout, you are temporarily suppressing your immune system?” the site claims. “As little as one hard workout can open you up to attacks by viruses and other diseases.” In an article, Wisdom to Live describes how the “window of vulnerability” in the hours after strenuous exercise can leave individuals unprotected from infection. The article advertises a dietary supplement it claims can protect the body during this time. Wisdom to Live did not respond to USA TODAY’s request for comment.
Researchers dispute `window' theory
The “open window theory” was established after marathon and ultra-marathon runners in the 1980s and ’90s reported illnesses in the weeks after races. The idea is that immune cells die after flooding the bloodstream following strenuous exercise, and that the decreased immune cells leave the body vulnerable for several hours. A study in the Journal of Sports Science and Medicine found marathon runners and elite athletes reported fewer annual sick days, indicating that exercise may have strengthened their immune systems. A study on mice in 2005 posted on the National Library of Medicine website found that moderate exercise in the days after influenza infection decreased mortality and prolonged exercise decreased survival, suggesting the impact on the immune system could vary by exercise difficulty. Researchers argued that taking on new vigorous workouts could weaken the immune system. “It is fair to say that a large increase in exercise intensity and/or duration, especially in people new to exercise, might have transient negative effects on the immune system,” University of Illinois Department of Kinesiology and Community Health professor Jeffrey Woods told The New York Times. According to a study in 2007 posted by the National Library of Medicine, most of the immune cells didn’t die but temporarily moved to areas that potentially would be most vulnerable to infection. The study questions the “open window theory” and suggests exercise “may enhance the immune vigilance in these compartments which serve as the body’s major defense barriers.” In 2018, a study by researchers John Campbell and James Turner from the Department of Health at the University of Bath challenged research supporting the “open window theory.” They determined there was insufficient evidence to support the theory because the runners’ illnesses were not laboratory-confirmed and their symptoms could’ve been the effect of unforeseen factors.
Our ruling: Partly false
Several studies found regular exercise promotes health and reduces risk of infections rather than increasing that risk. However, they do not definitively state that exercise has no effect on the immune system, and at least one study notes vigorous workouts could have a temporary negative effect.