Bone density: are muscles or gravity more important?

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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Earlier this year, I wrote a series of posts about bone density (see here, here and here), as well as a Jockology column on the topic. I started out with the assumption that maintaining strong bones is all about weight-bearing activity (which clearly makes no sense for, say, your arm bones), but after talking to some researchers, I learned that it’s our muscles, in fact, that place the greatest stress on our bones (which explains why our arm bones don’t wither away). But there were still a lot of conflicting studies about what type of activity is most important for bone health — whether, for instance, the smooth motion of an elliptical trainer or bicycle can help as much as the jarring motion of running.

So I was interested to see in the latest issue of Medicine & Science in Sports & Exercise a series of papers debating this very question, under the heading “Muscle Forces or Gravity–What Predominates Mechanical Loading on Bone?” (Intro here.) Basically, the answer is that we don’t know, and researchers are still arguing about it. It seems that gravity was long assumed to be the key, dating back to studies of bed rest in the 1920s and studies astronauts in the 1960s and 1970s. But there was a big shift in the 1980s:

Since 1987 when Harold Frost first proposed the “mechanostat theory” and began to assert that “Bone strength and ‘mass’ normally adapt to the largest voluntary loads on bones. The loads come from muscles, not body weight,” the notion has increasingly pervaded the literature.

Now, apparently, there’s a bit of a backlash from researchers arguing that gravitational loading — and in particular, sudden jarring like you get from hopping — is more important than previously suspected. I’m afraid there isn’t a nice, neat take-home message here. The researchers still don’t know the optimal way to stimulate bone growth, but it looks increasingly as if both muscular strength and weight-bearing activity have a role to play. So for now, cover your bases by doing both!

Jockology: exercises for strong bones

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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This week’s Jockology column (just posted) takes on a frequently asked question: What type of exercise is best for maintaining strong bones?

Once you reach adulthood, it’s basically one long fight against the slow but inexorable loss of bone strength – and the key to that fight, many of us assume, is weight-bearing activities.

But the latest research shows that resistance-training exercises like lifting weights can also play a crucial role in bone health – and in some cases are even more effective than weight-bearing activities such as elliptical training. [read the rest of the column…]

When my dad read the column this morning, he asked me if that meant that all the biking he does is no good for maintaining his bone strength. He’s correct that the research I presented suggests that biking isn’t as good as running (with its jarring impacts) or weight training (with its targeted strengthening of muscles) for bone health. But that doesn’t mean that biking, along with just about any form of exercise, can’t play a role in maintaining bone strength. I’d certainly rather that he spend an hour a day biking (which he enjoys) than grudgingly shift to doing leg weights (which he doesn’t enjoy) a few times a week.

For most people, bone strength is just one of the factors to be considered in designing an exercise program. Unless you’re at a high risk of osteopenia, I’m hoping the information in this column will help you make subtle tweaks in your exercise program, rather than a radical overhaul.

Bone density, this time for cyclists

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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Another new study on bone density, in this month’s Medicine & Science in Sports & Exercise. Since cycling isn’t weight bearing (except when you stand up out of the saddle), it’s often thought to be worse for building bone strength than alternatives like walking. And sure enough, the study I wrote about here found that competitive cyclists had lower spine bone mineral density than controls.

But the new study, from researchers at Manchester Metropolical University in the U.K., concludes that “sprint cyclists and to a lesser extent distance cyclists had greater tibia and radius bone strength surrogates than the controls.”

So, completely contradictory results from two studies measuring slightly different aspects of the same thing. Sounds like we don’t really know what’s going on yet (and don’t even know exactly which questions to ask).

Running and bone density: more info

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

Wow, research moves pretty quickly. Just a few hours after posting about the lack of good evidence that running helps bone density…presto! I get a press release about an article by University of Missouri researchers in the current issue of the Journal of Strength and Conditioning Research about how great running is for bone density. You can read the press release here:

In the study, the researchers determined the effects of long-term running, cycling, and resistance training on whole-body and regional BMD [bone mineral density], taking into account the effects of body weight and composition, in men ages 19 to 45. After adjusting for differences in lean body mass, the researchers found that runners had greater spine BMD than cyclists.

This still doesn’t tell us explicitly about how activities like elliptical training, which are weight-bearing but not high-impact, affect bone density. The University of Missouri researchers seem pretty convinced that the jarring action of running (or jumping around by playing basketball, for example) helps bone density. The question is, how much?

Elliptical training and bone density

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

In the wake of the column comparing elliptical training to running, I got a very interesting e-mail from Gary Rothbart, a Toronto personal trainer. He said, in part:

I feel that the fitness community has done a great disservice to the average person. One of the most important factors with respect to avoiding osteoporosis is high impact activities… The difference between running and the use of non-impact machines is great when taking into the long term implications on bone density.

That makes a lot of intuitive sense. To be honest, that’s something I expected to find when I started researching this story — but I didn’t. Continue reading “Elliptical training and bone density”