Can too much of a healthy habit become bad? Lots of evidence shows that regular exercise wards off respiratory infectionslike colds, flu, and COVID-19. However, very vigorous exercise may lead to these infections by triggering immune changes that increase risk, according to a new study. The findings come as we enter another possible tripledemic this winter, with an increase in COVID, flu, and respiratory syncytial virus (RSV). Public health officials are on alert for a potentially severe flu season, following high flu activity this year in Australia (which can help predict how bad the US flu season will be).
Studies show that the risk for acute respiratory infections is lower in people who exercise regularly. Physically active people are also less likely to suffer severe outcomes from COVID. But while inactivity has emerged as a potential risk factor for respiratory infections, scientists have long proposed that too much activity, particularly of a prolonged and highly intense nature, may also increase susceptibility.
“The theory suggests that a short-term suppression of the immune system following intense exercise leads to an increase in susceptibility to infection, especially upper respiratory illness,” said Choukri Ben Mamoun, PhD, professor of medicine (infectious diseases) and microbial pathogenesis at the Yale Institute for Global Health, New Haven, Connecticut. Researchers have documented a greater incidence of upper respiratory illness “among both highly trained and healthy untrained individuals following increased activity during competition or heaving training blocks.”
Excerpted from Medscape