Exercise and Your Immune System: Warding off H1N1 One Dead Rodent at a Time

Does exercise really boost your immune system? Two new studies examine this connection and the results are not as clear cut as everyone would like to believe.
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Exercise boosts your immunity. It's one of the most touted reasons for getting a good sweat on and in this season where the H1N1 virus has become more popular among school kids than Miley Cyrus, this factoid is getting more play than Jude Law. But is it true? Does exercise really boost your immune system? Two new studies examine this connection and the results are not as clear cut as everyone would like to believe.


When I first fell in love with regular exercise and healthy (or healthier, anyhow) eating in my early 20s, one of the first things I noticed was rather than the 6 or so colds I'd been getting every year I was now only getting one or two. This was especially exciting as I'd watch my non-gym buddies drop like flies all around me while I remained hale and hearty because there's nothing I love more than some nice schadenfreude on a cool fall day. In all seriousness, people began to ask me why I never got the bugs going around and I was more than pleased to tell them "healthy living."

A few years later down the road of hubris and kids in that germ-incubator we call school had me singing a different tune. Suddenly I was getting more of the sickies although I was still proud to note that most of the time the case was pretty mild. This was also the time when I started to really ramp up my exercise (see GFE supreme failure double cardio). But I thought nothing of it because I knew -- fallacy alert! -- that the more I exercised the healthier I was. Still, I never quite made the connection.

Mice are smarter than I am. Well, research mice anyhow. This past week two studies were reported in the New York Times examining the effects of no exercise, moderate exercise and high intensity exercise. Both experiments involved little mice running on twee treadmills (adorbs!) and then being exposed to a lethal-to-mice flu virus. Researchers found:

"'A J-shaped curve' involving exercise and immunity. In this model, the risk both of catching a cold or the flu and of having a particularly severe form of the infection 'drop if you exercise moderately,' says Mary P. Miles, PhD, an associate professor of exercise sciences at Montana State University and the author of an editorial about exercise and immunity published in the most recent edition of the journal Exercise and Sport Sciences Review. But the risk both of catching an illness and of becoming especially sick when you do "jump right back up" if you exercise intensely or for a prolonged period of time, surpassing the risks among the sedentary."

This whole moderation thing makes sense to me -- in theory of course, you know how I am -- but it is that last sentence that really tweaked my interest. Could intense exercise -- defined as "a workout or race of an hour or more during which your heart rate and respiration soar and you feel as if you are working hard" -- really be worse for your immune system than being sedentary? I would think that of all three groups, the lazy mice would have fared the worst.

Not true say hundreds of ghostly rodents. The second study found, "more than half of the sedentary mice died [after being exposed to the flu virus]. But only 12 percent of the gently jogging mice passed away. Meanwhile, an eye-popping 70 percent of the mice in the group that had run for hours died, and even those that survived were more debilitated and sick than the control group." Lest mice aren't convincing enough, researchers also tested the level of immunoglobulins, substances that fight off infection, in the saliva of professional athletes. These researchers concurred with the rodents saying, "the longer the duration and the more intense the exercise, the longer the temporary period of immunosuppression lasts -- anything from a few hours to a few days."

So what's a sweat-lovin' guy or gal to do? Especially if you are signed up for a marathon or other long immunosuppressing race this season? Some suggestions to prevent illness (also known as the OCD Christmas list):

  • Wash your hands often
  • Carry hand sanitizer (and use it)
  • Don't touch your face
  • Wipe down equipment at the gym both before and after using it
  • Make sure your diet includes plenty of fresh fruits and veggies
  • Get adequate sleep
  • Get a flu shot, if you're into that kind of thing
  • Stay home and rest if you have a fever, sore throat, body aches or sprout a curly tail
  • Take it easy on the exercise if you just have a cold (You've heard the rule: if it's above the neck, you're okay to work out gently; if it goes below the neck then stay the heck away from the rest of us you psycho.)

There. I'll stop being your mom now. Anyone else surprised by these studies? What are your tips for staying healthy this season? What has been your experience with your exercise and immune system?

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