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Dear List,

And here's the research summary on exercise for bones:
One list member challenged me to provide a reference to a Jane Brody  
column (New York Times) I cited in which she said weight-bearing  
exercise does not, per se, build bone. I couldn’t find it, so I wrote  
Brody and amazingly, she answered! She doesn’t remember saying any  
such thing. Challenges are good; they lead to better and stronger  
information.

Here’s what Brody wrote:

“….the tug of large muscle groups on bone is what stimulates bone  
strength, and the way you get that is thru regular weight-bearing  
exercise. Preventing falls by improving balance reduces the risk of  
fractures, especially in people whose bone density may be deficient.”

I also asked an ob/gyn friend about how exercise makes bones stronger.  
He said the slight injury produced by aerobic exercise causes the body  
to marshal its repair functions, so that just as a broken leg becomes  
stronger in the spot where the break occurred, so are bones slightly  
injured by exercise.

In addition, I did some on-line research into the question, but didn’t  
find many scholarly articles I could read w/out paying a fee. The  
upshot of my search, however, is a feeling that there is some  
scientific controversy about exactly how exercise makes bones  
stronger, not to mention controversy about the real meaning of bone  
densitometry results (bone density is what we can measure, not  
necessarily what matters). Below, the urls.

1. A nice primer on how bone regeneration works

http://courses.washington.edu/conj/bess/bone/bone2.html



2. There is a history of studies showing that exercise does prevent  
help bone loss and/or reverse it. For instance, a meta-analysis of  
studies from 1966 through 1996 on exercise and bone loss:

“The weighted OTs (overall treatment effects) for the RCTs   
(randomized controlled trials) showed very consistently that the  
exercise training programs prevented or reversed almost 1% of bone  
loss per year in both LS (lumbar spine) and FN (femoral neck) for both  
pre- and postmenopausal women.”

  http://www.springerlink.com/content/ywv4w3m54tfx5kt0/



3. However, other, post-1996, studies argue the claim. I’ve spent  
quite a number of hours on this, and cannot find many articles that I  
can access for free, so I don’t know what’s in some of the scholarly  
work that shows up in a Google search. But for whatever it’s worth:

  abstract of 1999 article

“….the rate of bone loss for postmenopausal women can be slowed by  
exercise, should be viewed with great caution: there was only a  
partially significant finding that strength exercises provided this  
benefit in the group calculations, and other statistically-significant  
results were obtained by the exclusion of certain groups of  
participants.”

http://www.library.nhs.uk/womenshealth/ViewResource.aspx?resID=240004



4. 2001 publication testing effect of exercise plus alendronate  
(Fosamax) in women early in menopause (when bone loss is high)

“Exercise alone had no effect on bone mass at the lumbar spine or  
femoral neck; it had neither an additive nor an interactive effect  
with alendronate at these bone sites. However, at the distal tibia the  
mean increase of 3.6% (0.3–7.1%) in the section modulus (that is, bone  
strength) and 3.7% (0.1–7.3%) increase in the ratio of cortical bone  
to total bone area were statistically significant in the exercise  
group compared to the nonexercise group, indicating exercise-induced  
thickening of the bone cortex. Bone turnover was reduced in  
alendronate groups only.”

  http://linkinghub.elsevier.com/retrieve/pii/S8756328203000826



5. bone density an insufficient measurement to predict fracture risk;  
abstract of paper that makes a distinction between bone density and  
overall bone quality



http://www.ncbi.nlm.nih.gov/pubmed/15763602?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&linkpos=2&log$=relatedreviews&logdbfrom=pubmed



6. “….indicate that bone loss is not a constant process over time but  
rather exhibits cyclical damping oscillations.”

http://linkinghub.elsevier.com/retrieve/pii/S8756328202009018



7. and on a completely different note:

  “The bone remodeling response to exercise training in women not  
taking HRT was not significantly different from those not exercising.  
However, the direction of change suggests an elevation in bone  
remodeling in response to exercise training, a phenomenon usually  
associated with bone loss.”



http://www.ncbi.nlm.nih.gov/pubmed/12574871?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&linkpos=5&log$=relatedarticles&logdbfrom=pubmed



I have tried (above) to stick to scientifically reliable references.  
In searching for relevant information, I’ve read myriad articles  
claiming this or that. But when I check the medical researchers  
mentioned in those non-medical articles, it generally turns out the  
non-medical writer has shamelessly cherry-picked. For example, one  
sensible-sounding website article cites a meta-analysis of research on  
the efficacy of calcium for bones, and says the research shows that  
it’s Vitamin D that counts, not calcium. Hmmm. What the researchers  
actually say, in their abstract,

  "Subgroup analyses suggested that the effect size was independent of  
calcium supplementation, type of vitamin D, duration of therapy, and  
sex, but reduced sample sizes made the results statistically  
nonsignificant for calcium supplementation, cholecalciferol, and among  
men."

http://jama.ama-assn.org/cgi/content/abstract/291/16/1999

  In addition, the study is now 10 years old.

  Bottom line: there is significant scientific controversy about what  
works and what does not.



cheers,

Mary B.
NYC
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