Exercise Protects You From Colds

Posted on 04 Nov 2009 22:18

Well, at least it does according to this article by ACSM which claims that, according to David C. Nieman, DrPH, FACSM, "multiple studies have shown a 25- to 50-percent decrease in sick time for active people completing at least 45 minutes of moderate-intensity exercise (such as walking) most days of the week."

Right here we have a good lesson in how to spot BS. When an article mentions "multiple studies" without ANY references it is almost always bullshit. Try to find "multiple" studies that show this, I dare ya. I double dare ya. You can say that the article is "referencing" this Niemen fellow. I call that "hearsay". If Nieman had written it in a REFERENCED article or book, that would be a better "reference". See what I'm saying? When we write we have a choice between "journalism" and research. Sometimes they are one and the same. Sometimes they are not.

Nieman is likely referring to his own studies. Which are most likely based on the shotgun method and perhaps a little salami slicing. And while his survey studies certainly do seem to show that those who engage in moderate exercise spend more time at work, this hardly proves what the article claims, that exercise "protects" one from colds. And Nieman's studies on actual immune function in athletes versus non-athletes certainly show no credible effect.

Exercise builds immunity is pretty much common belief. And many trainers, coaches, etc. assume it to be true without EVER having seen any direct scientific evidence for it. And in fact, there is no real evidence. As far as can be determined, the immune factors in well-trained athletes, moderately trained people, etc. and so on, are well within the normal range. Endurance athletes are more prone to UTRI's as a matter of fact (upper respiratory infections). Whether this is from over-training or simple airway irritation remains to be seen. And how over-training effects immunity remains to be seen in general although it is generally assumed that over-training results at least temporarily in a reduction but there still have not been enough studies on this.

There simply is very little evidence to suggest that there is any clinically significant difference in immune function between sedentary and moderately active persons. Statements to the contrary rely on epidemiological evidence. And none of this evidence, which seems scarce, that regular moderate exercise actually enhances immunity compared to sedentary individuals. Still, this post is not about "immunity" per se, but the claim that "exercise reduces sick leave" and especially about the main premise of the article, that exercise protects you from colds.

Here is a question you may not have asked. Does sick leave really have anything to do with the claim that exercise protects against colds?

I've tried to find these MULTIPLE STUDIES showing that exercise reduces sick leave and I'm coming up a bit short, to say the least. I've HEARD of ONE study in the Netherlands, which I will talk about later on.

What I AM finding are studies showing a reduction in sick leave due to specific chronic pain complaints. Like this one about neck pain:

And these studies about THERAPY for low back pain which I guess a "creative" person could have chosen to think of as exercise:

Maybe this one about water aerobic and back pain from pregnancy could have been stretched a little:

So you probably get the point. Those studies are specific to chronic pain and programs (involving exercise) designed to reduce that pain, thus reducing sick leave time.

I'm not saying that these studies are some of the multiple studies the ACSM is talking about but I will tell you this: Don't be surprised if they were! I've been doing this a long time and if there is one thing I have seen more than any other in "scholarly articles" is what I call reference padding. This is when an author "pads" the references for his article with many, sometimes 50 to 100 references that have very little or nothing to do with the subject of the article, but simply have a loose association. For instance, you write an article about protein and you cite 50 studies that mention the word protein. These authors are counting on the fact that 9.9 people don't check the reference. I am the .1 person who does.

So let's be clear. The name of the article is Protect Against Colds with Exercise. The authors are implying that sick leave from VIRUSES such as the cold is reduced by exercise.

The ACSM article didn't even bother with references. Which means we can disregard it. Which I would except for the fact that it is a good lesson in BS detection. Shall I go on? I mean, I bet you thought exercise reduces colds and flus didn't you? Well, let's find these studies.

Here is that study from the Netherlands I mentioned early on:

Dose-response relation between physical activity and sick leave

Based on surveys and "databases" we get some results that I bet the ACSM wouldn't want included in it's "45 minutes of moderate-intensity exercise (such as walking) most days of the week" guidelines.

This study found no benefit from "moderate physical activity" but did find benefit from "physical activity at a vigorous intensity level for at least three times a week" and it further mentions that duration had no effect.

That is the only study I have been able to find thus far and it is a long way from proving the statement "exercise reduces sick leave" and doesn't even come close to showing that exercise protects you from colds. It only shows, that in this study, they found a correlation between reduced sick leave and vigorous physical activity. One study doesn't mean much but even it does show anything there was no data on what the sick leaves were or were not from. People miss work for a lot of reasons.

So perhaps you see the "jump" the authors made here. Exercise reduces sick leave is not the same thing as exercise protects from colds unless we are so mind-numbingly naive we think that people routinely miss work because of a head cold. I've missed more work due to, yep, debilitating lower back pain, all told, than I ever have from cold and flu.

And what about the exercise and pain connection? Can you, for instance, cure your lower back pain with exercise. To some extent, you can make your lower back and non-issue through a very focused and proper exercise routine. Many times, however, people just get off the couch, start exercising pretty much randomly and start noticing a fairly profound effect on their pain, and thus the frequency of sick leave. The bad news is this effect rarely lasts.

You've probably heard, for instance, general statements about the positive effects of exercise on lower back pain and sciatica. The idea being that just doing some walking every day is good for both non-specific lower back pain and sciatica. Really, though, it's a default statement. What is really BAD for those conditions is prolonged bed rest. Therefore telling people that "exercise helps" is more of a can't hurt, may help" kind of thing and is much better than lying in bed all the time. Keep in mind that I am talking about general exercise and not exercise programs specifically designed to benefit these conditions.

But let's turn this thing around and ask about the connection between vigorous activity, pain, and sick leave. Compare that with moderate activity, pain, and sick leave. Is there is a difference between those who engage in vigorous exercise and those who engage in moderate exercise? I'd say there is. Would that difference, perhaps, influence the amount of sick leave these different people take independently of how often they are sick or in pain? It is certainly possible that it could.

Can one study about sick leave ask enough questions to really show how much effect exercise has on sick leave? NO. Can multiple studies prove it? NO. But not for the reasons you may think. The reason that multiple studies can't prove it is because studies aren't about "proving" things. They are about disproving them. In this case, the "theory" is that exercise reduces sick leave". It neither has enough support from reliable data to be taken seriously nor has enough evidence against it to be called rubbish. It could be true but there is no reason to count on it being true.

When it comes to the article in question, however, we must ask if ANY evidence has been presented to support the statement that exercise protects you from cold. And none WAS given.

I would tend to assume that regular exercise means less missed work. Whether there are multiple studies proving this or not it's clear that "exercise makes us feel better" through VARIOUS mechanisms. Reduced pain, better mood and fewer mood swings, more energy, etc and so on. There is some science to back this up and there is a lot of "anecdote" as well. Exercise is HEALTHY. Most people are on board with that…even those who call it a "necessary evil". But to say that exercise makes our bodies more immune to pathogens like the cold is a stretch that needs SOLID science to back it up. And the science is not there.

Studies that depend on surveys concerning exercise frequency, perceived fitness, and sick leave from URTI's or "colds" seem to show a correlation between moderate exercise and less sick leave. However these types of studies should be taken with a grain of salt because they cannot show a cause and effect relationship between fitness and frequency of colds. It may well be that those who feel sick less often exercise more! In other words, the amount of time people spend exercising is just as likely a consequence of their state of health. It is also possible that those who are more active report on symptoms differently than those who are sedentary. Yes, maybe people who exercise more WHINE less about things like a case of the sniffles. There are too many confounding variables in these studies. On the other hand, studies which actually attempt to measure immune function in show no significant difference.


1. Gleeson M., Immune function in sport and exercise. J Appl Physiol. 2007 Aug;103(2):693-9. 2007 Feb 15. webcite <http://jap.physiology.org/cgi/content/full/103/2/693>

2. Kreider, Richard B., Andrew C. Fry, and Mary Louise. O'Toole. Overtraining in Sport. Champaign, IL: Human Kinetics, 1998. Print.

3. Nieman, David, Et Al. "Upper Respiratory Tract Infection Is Reduced in Physically Fit and Active Adults British Journal of Sports Medicine 2010 BMJ Journals. Web. 05 Nov. 2010. <http://bjsm.bmj.com/content/early/2010/09/30/bjsm.2010.077875.abstract?sid=bc6e3fe4-0dd0-440d-b497-226efbddf452>.

4. Nieman, David, Et Al. "Immune function in female elite rowers and non-athletes" British Journal of Sports Medicine." British Journal of Sports Medicine 2000;34:181-187. British Journal of Sports Medicine - BMJ Journals. Web. 05 Nov. 2010. <http://bjsm.bmj.com/content/34/3/181.abstract?sid=bc6e3fe4-0dd0-440d-b497-226efbddf452>.

This page created 04 Nov 2009 22:18
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