Women recover muscle strength more slowly than men

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Women recover muscle strength more slowly than men

http://www.eurekalert.org/pub_releases/2008-09/ou-wrm092508.php

Women's muscles may require longer, more intensive rehabilitation

after bed rest and cast immobilization, as reported today by the

Institute for Neuromusculoskeletal Research at the Ohio University

College of Osteopathic Medicine (OU-COM).

According to C. , Ph.D., assistant professor of

neuromuscular biology, the discrepancy may relate to how sex-specific

hormones regulate the growth of muscle mass. The study is the first

to report sex differences in muscle strength restoration following

immobilization of a limb.

" Our findings may have important implications for how women are

treated for fractures, including more and/or different rehabilitation

methods, " said.

worked on the study with Ohio University researchers L.

Hoffman and W. Russ, Ph.D., as well as Todd M. Manini, Ph.D.,

of the University of Florida. The team discussed their findings this

week at the Integrative Biology of Exercise meeting, hosted by the

American Physiology Society (APS) in Hilton Head, S.C. A report of

their preliminary data will appear in an upcoming issue of Archives

of Physical Medicine and Rehabilitation.

The researchers set casts to the non-dominant wrists and hands of 10

healthy volunteers – five men and five women – for three weeks. Wrist

muscle strength was measured prior to placement of the casts, weekly

during immobilization and one week after cast removal. Researchers

also used electrical stimulation to induce muscle contractions, which

showed how well the participants' nervous systems were able to

activate their wrist muscles.

Results showed that men and women lost muscle strength at similar

rates during immobilization. But within one week of cast removal, the

men's strength returned almost to pre-cast levels, while the women's

strength levels remained 30 percent lower than normal.

Immobilization did reduce the ability of the nervous system to

activate wrist muscles, and the response was similar in men and

women, suggesting that the slower restoration of strength among women

is more likely due to different rates of muscular strength-building,

as opposed to differences in the nervous system.

According to a 2003 World Health Organization report, women are four

times more likely than men to experience forearm fractures requiring

cast immobilization, and almost 50 percent of women will experience a

bone fracture at some point in their life.

cautioned against over-interpretation of the study results

because of the relatively small sample size. " Our findings indicate

that more work needs to be done to confirm and understand the reasons

for these sex differences, the extent to which they occur, and the

underlying mechanism, " said.

and his colleagues have begun the next phase of this research,

which they hope will provide more comprehensive answers.