Originally Posted by
AlmostTrick
I've always suspected this, and have noticed myself becoming more susceptible to getting sick the day after an overly intense martial arts workout, but never from a bike commute, even though I like to crank it up fairly high for almost an hour each way. I think the difference is what your body is accustomed to.
Yeah, there are too many factors. The actual exercise does seem to depress immune function, but at the same time, people who engage in regular exercise are probably somewhat more likely to take care of themselves in other ways (eating properly, good sleep habits, etc.). When it's all added up, whether it makes you more or less likely to get sick is a tossup.