June 06, 2014
How Much is "Too Much Exercise?"
Guest Post by Tiffany Reiss
Can exercise actually be bad for your health? And how much is too much? It's a complicated issue, and, sadly, requires more than a quick google search to answer. So, being lazy, I thought I'd let Dr Tiffany Reiss take it and run with it! (Though not too far or too fast, as we wouldn't want her to hurt herself.)
As you may recall, Tiffany is an an exercise physiologist and adjunct faculty member at Seattle University, Lake Washington Institute of Technology, American Public University and Walden University. She is also a contributor for the Sports and Fitness Network and the co-founder of TheHubEdu: A Learning Library.
Please welcome Dr. Tiffany Reiss for another guest post!
Recently more and more articles are appearing in the news, warning of the dangers of too much exercise. Studies have suggested that endurance athletes may damage their health running more than 30 miles a week, that ski marathoners may be more likely to have certain heart problems, and that high mileage runners may have shorter lifespans.
Now this is not a problem many of us need to concern ourselves with in the big picture of our lives. I wish this were an issue I needed to address in my own life, too much exercise. But alas, most of us, myself included, are on the other end of that spectrum, too little exercise and a struggle to even make it to that point. Still, as an exercise physiologist, I have to wonder what might constitute “too much” exercise and what happens physiologically that can actually be dangerous.
Let’s start with stress. I think what’s important to remember is that exercise is actually imposing physical stress on the body. Stress is good in this context. We now better understand we need to stress (or challenge) the body in order to grow stronger, leaner, faster.
How much is too much stress from exercise? That seems to depend on how intense, how frequent, and how long the activity is. The stress imposed on the body via exercise is actually what forces positive physiological adaptations, even at the genetic level. We all know the positive benefits of regular exercise. So if a little is good, a lot must be better, right? Well, up to a point.
There is ample evidence that engaging in regular, moderate, physical activity actually slightly enhances immune function in the short term making those individuals less likely to become ill (and could also play a role in chronic disease prevention). This is one of the many benefits of regular exercise and it’s linked to an overall long-term decrease in inflammation in the body.
On the other hand, too much exercise, even at one time (high intensity, long duration) can actually cause immunosuppression making acute illness more likely, and potentially leading to an increase in inflammation in the body long term. It sounds contradictory since inflammation is technically immune function response, but we are talking about short-term acute responses versus long-term chronic adaptations.
While regular, moderate exercise can cause a short-term increase in inflammation (immune response), it may also result in a long-term chronic adaptation of lower inflammation in the body, which is good. In contrast, high intensity, long-duration activity has the opposite impact, potentially leading to long term inflammation. Unfortunately, low-grade inflammation is linked to pretty much all chronic diseases at this point.
It's important to understand that there is a dose-response relationship from a health versus fitness perspective. Evidence suggests from a “health” perspective that accumulating about 150 minutes of moderate physical activity per week is the optimal dose needed for optimal health and accumulating much more does not seem to have any significant impact on health outcomes. (For example, Dr. James O’Keefe, director of preventive cardiology at the Mid-American Heart Institute, suggests that running at a slow to moderate pace two to three times each week for a total of about 150 minutes seems to be a "sweet spot.")
However, ultimately what is considered intense or moderate activity is highly individualized.
If I briskly walk or trot for 150 minutes per week, from a health perspective I am setting myself up for the best possible outcome. Am I fit if I do this? Well, I am more fit than my sedentary counterparts but would I then feel comfortable going out and running a 10k race. No? I would not be “fit” enough to do that well.
And guess what? If I did decide to just go out and a run a 10k race one Saturday, the duration and intensity of that just might throw my immune system into a compromised position for a day or so because relatively speaking, that would be too intense and too long (too much stress). Could I train for that race so my body would not consider that such a stress? Yes.
But then it gets complicated: What are the long-term consequences of constantly and repeatedly stressing my body to the point I can run 10k’s, half-marathons, marathons, ultra-marathons? Is all this exercise (stress) cumulative at some point? If I continue to train and train and damage my body (because of the stress) does this ultimately take a toll on my muscle tissue including my cardiac tissue (evidence suggest it might)? Could I actually damage my body by not allowing it to rest enough?
Other factors may have an impact too: Do genetics play a role here? Probably. Body-type? Probably. Age? Definitely. Body weight? Probably. Overall health status? Probably.
What makes this so tricky is the highly individualized nature of what is “optimal” and it is likely a little different for every single individual. But the good news is: there is an optimal level for everyone and just like everything else, it comes down to moderation.
Can I train for and run (being a generous term here) a ½ marathon a couple times per year and still be fit and healthy? Of course. Should I train for and run ½ marathons every month for years? I could, and I would be very fit, but I think there might be some long-term potential health consequences for that choice. But that’s just me and my body, someone else might be just fine engaging in that level of activity…it might be optimum for them.
Bottom line, moderation is key. Too little exercise, not good. Too much exercise, not good. There is likely an optimal level for everyone, but it might not be the same from person to person. The key is to disrupt homeostatic balance, but not so much and so frequently the body doesn’t have time to heal. Most of us rest too much and exercise too little, but there is a percentage out there that might just not be resting enough and this can potentially have long-term health consequences.
Note from Crabby: For some reason, this post is getting assaulted with spam so I am closing comments. Sorry!