There is still a lot to learn about how exercise affects the immune system, because it's difficult for researchers to assess the many layers of protection within the system. Strenuous or prolonged exercise seems to suppress the immune system, leaving athletes more susceptible to illness for one to six hours following a hard workout - the so-called open window.  -   Michael Flynn     Quotes
There is still a lot to learn about how exercise affects the immune system, because it's difficult for researchers to assess the many layers of protection within the system. Strenuous or prolonged exercise seems to suppress the immune system, leaving athletes more susceptible to illness for one to six hours following a hard workout - the so-called open window. Michael Flynn
 Exercise