Human Limits

Exploring performance and health with Michael J. Joyner, M.D.

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Too Much, Too Much Exercise?

There has been yet another wave of “too much” exercise stories in the media based on a recent study of 1 million women from the UK. The idea is that moderate levels of physical activity most days with occasional bouts of strenuous activity can cause big drops in both cardiovascular and all-cause mortality. However, doing a lot of hard training is not as beneficial.

This topic has been recycling for the last couple of years. Alex Hutchinson (who has a Ph.D. in physics) has done an excellent numerical/statistical breakdown on one of the key studies that “supports” the too much exercise hypothesis. Put simply there are many limitations to the whole argument. I have done a couple of posts on what both the epidemiology and physiology tell us on the topic. The first was in 2012 and another one with Brad Stulberg in 2014. I too am a skeptic.

I am in the camp that 30-60 minutes of physical activity most days is the sweet spot for general health and that more is not better, but it is not worse either. Those who really push it most days are also likely motivated by things other than return on investment thinking about their health. Perhaps they want to compete in races or are into pushing themselves to meet more hard core physical goals.


The Swedish Skiers

Whenever this topic comes up I also bring up a paper that followed about 50,000 male finishers of the 90km (~55 miles) Vasaloppet cross country ski race in Sweden. This study used the Swedish medical records system to look at mortality in the race finishers. In preparing for an upcoming talk on exercise and health, I asked my colleague Andy Miller to generate some figures from the skiing study. The one below shows that mortality is about 50% or less than predicted for race finishers compared to the expected rate gleaned from Swedish population records. It also shows that finishing more races was not associated with an uptick in mortality, if anything it was associated with a down tick. Who knows exactly what these folks were doing, but those who finished a number of races certainly had to be doing a lot of strenuous training over many years.






I have repeatedly asked those in the “too much” much camp to rebut this paper and point out any major flaws in it.   The bottom line is that it is at least as strong or stronger than the studies “supporting” the too much exercise hypothesis. Until data comes along that clearly refutes the data in the chart above I will remain a skeptic.


2 Responses to “Too Much, Too Much Exercise?”

  1. March 26th, 2015 at 11:47 am

    JustaTech says:

    When i think about the issue of “too much” exercise I think about TV shows like “Biggest Loser” where people who are seriously overweight and not in good cardiovascular shape are pushed to exercise very hard for many hours a day. So if you’re not in good health to start with and then you jump straight into a super-intense training program, beyond what most professional athletes would do, then yes, too much exercise could be very bad for you.

    But for average people exercising in moderation? I agree that the data is pretty questionable.

    (90k in less than four hours some years? Dang that’s fast!)

  2. October 31st, 2015 at 10:17 am

    Larry Licklider says:

    Bodily activity typically involves gravity working on body’s center-of-gravity, effecting endothelium (wall) shear stress that mediates vessel caliber changes within circulatory paths. Outcomes include more exchange of oxygen and other factors due to enhancements to microcirculatory perfusion, without an obligatory Increase in heart rate and cardiac output. The opportunity of allowing gravity to work on vessel walls to activate endothelial nitric oxide can be pursued without increasing extent of muscle contractions beyond a very gentle range that even exercise-intolerant individuals are capable of.
    While requirements for exercise-mediated contractions can remain low, I assume that need for ‘moderation’ is met, for so long as bodily stress remains inconsiderable. The beneficial activation within circulatory paths can have effects that accrue over time in absence of limiting stress due to inelastic forces acting on our heavy bodies.
    Question of whether too much exercise is possible can be split into questions of what type of exercise and what outcomes accrue from increasing the exercise.

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