One more reason to shake a leg

How often do you exercise?

According to research just published in the British Journal of Sports Medicine, people who reported that they exercised at least five days a week suffered far fewer colds and other upper respiratory tract infections than people who exercise one day a week–or less. To be technical, they spent 43 percent fewer days sniffling, sneezing, etc. And the symptoms the regular exercisers did have tended to be less severe than those of their couch potato peers.

Some of this effect may be mind over matter, because those folks who rated themselves as “highly fit” fared 46 percent better than those who reported that they had low levels of fitness.

So why is this? Well, that’s not clear. It’s well known in scientific circles that our immune systems get a boost for a few hours every time we get a dose of good, moderate aerobic exercise (biking, brisk walking, jogging, eliptical trainer, etc.). What happens is that a bunch of the cells that do the heavy lifting in our immune system (tracking down and killing nasty invaders) kind of get recirculated post-exercise.

What’s not certain is how those immune-boosting effects might linger. Even though the immune system returns to pre-exercise levels a few hours later, researchers think that each time we exercise, we might improve the surveillance abilities of our immune system cells.

To try to make sure that some other lifestyle factor wasn’t really responsible for the difference in the infection rate, the researchers did adjust their results to take into account things like age, gender, education, marital status, mental stress, body mass index and fruit intake. The were not able to factor in differences in how many viruses and other pathogens the participants were exposed to at work and home (yeah…that’s a tricky one to manage).

This study does not suggest that exercise is a magic bullet for avoiding annoying winter illnesses. All the study shows is that there is an association between regular exercise and fewer sick days. It doesn’t say “If you exercise 5+ days a week, you will have fewer respiratory infections.” It also does not explain how regular exercise might make people more resistant to colds and other ick.

But so what. We should all be getting regular exercise anyway, right?


If it does turn out that there is some yet-unproven cause and effect, then bonus points to you for doing the healthy thing in the first place. And if wanting to avoid stocking up on tissues this winter prompts you to keep on exercising (or to get started), then that’s fantastic. Truly. You’ll be a better person for it.

Photo: © Derek Abbott |