Microscopic damage to the muscles from running a marathon can cause more
than soreness. The muscle damage incurred from running a marathon can divert
some immune cells for muscle repair and weaken others, leaving the immune
system less able to protect against upper respiratory tract infections.
While there is no direct evidence that those runners with the most weakened
immune system are those who develop upper respiratory tract infections there
is evidence of a higher rate of it in marathon runn
