Exercise only preserves the muscles you actually use


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- Alex Hutchinson (@sweatscience)


It was great to see the big response to the MRI pics I posted a couple of days ago showing the well-preserved leg muscles of a 70-year-old triathlete. Very striking stuff. But let me now offer the following caveat:

This is a figure from a new study from the University of Western Ontario, just posted at Medicine & Science in Sports & Exercise. They analyzed the biceps brachii (arm muscles) of nine young runners (average age 27), nine old non-runners (70), and nine lifelong masters runners (67). They measured the number of functional motor units (i.e. group of muscle fibres activated by a single motor neuron), which typically declines with age. As you can see, the two old groups were pretty much the same, far below the young group.

In contrast, the same researchers studied leg muscles (tibialis anterior) in a similar group of volunteers last year (as I blogged about here) — in that case, the older runners did preserve the number of motor units. What this tells us is that exercise, on its own, doesn’t preserve all the muscles in your body: in the words of the researchers, there’s no “whole body neuroprotective effect,” or at least none that shows up in this relatively small study. It just preserves the muscles you’re using on a regular basis. So that’s still good news for triathletes, but maybe not as good for runners and cyclists!

7 Replies to “Exercise only preserves the muscles you actually use”

  1. This seems like it should be obvious, but it seems culturally we are happy with getting any sort of exercise that we assume it will just make everything better. I know people that run that never pick up weights, and I know people that are the opposite. This research should be much more prominent than it is to encourage more full-body health.

  2. Thanks for sharing this. Great breakdown. I agree with Marshall, that this seems like it should be obvious. I wrote a blog about this topic not too long ago. I read a literature review by Phillips & Winett published in Current Sport Medicine Report in 2010 where they were lobbying for a public health mandate to encourage folks to do more strength training for the health benefits. They also discussed sarcopenia and the effects that strength training and aerobic training have on it. Hope you don’t mind if I share the link: http://www.timarndtfitness.com/2012/02/02/7-reasons-you-have-to-strength-train-2/.

  3. It looks like Nordic Walking has some merit after all. It is a full body exercise. Running is great for the heart and bone density, but what is the point if you are as weak as a kitten. 50 percent of your muscle mass is above the waist. After chasing the mastodon or deer like creature, we had to have upper body strength to spear it or kill it. Another benefit of cross fit or too extreme?

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