Women do not recover their muscle strength as fast as men

Women are four times more likely than men to experience a broken forearm and require a cast (immobilization). To examine whether the effects of casting were similar between the sexes, researchers examined immobilized volunteers for a period of three weeks. They determined that while men were able to regain 99% of their strength within a week of removing the cast, women's strength was still 30% lower when compared to before the cast was applied. These finding may have implications for the treatment of fractures based on gender lines. The study is believed to be the first report of sex-differences in muscle strength restoration following disuse. It was conducted by Brian C. Clark, Richard L. Hoffman, and David W. Russ of Ohio University, Athens; and Todd M. Manini of the University of Florida, Gainesville. The researchers will discuss their study, "Restoration of Voluntary Muscle Strength Following 3-Weeks of Cast Immobilization Is Suppressed in Women Compared to Men," at the American Physiological Society (APS) (www.The-APS.org) conference, The Integrative Biology of Exercise V. The meeting will be held September 24-27, 2008 in Hilton Head, SC. The journal Archives of Physical Medicine and Rehabilitation has also accepted a 'brief report' of this preliminary data for rapid publication.

The Study

Ten healthy volunteers completed three weeks of forearm immobilization (5 females, 5 males; 18-29 years of age). The subjects were fitted with a forearm cast on their non-dominant arm and each persons wrist muscle strength was determined weekly during the immobilization phase, and a week after the casts were removed. The measurements taken prior to the casting were repeated to detect any gender differences that may have developed over the course of splinting or recovery.

Results

The research team found:

• men's strength had returned to baseline levels one week after the cast was removed;

• women's recovery levels were significantly lower, one week after the cast was removed they still exhibited strength deficits of approximately 30% below baseline. All the women exhibited a slow recovery of their strength (at least a 15% reduction relative to baseline); whereas only one of the men showed a similar deficit.

Conclusions

In explaining possible reasons for the discrepancies, Dr. Clark suggested that hormones, and the role they play in regulating muscle mass, may contribute to slower recovery times in women. According to Dr. Clark, "This finding is preliminary and on a very small sample size, so, we must caution against over-interpreting our work. However, it certainly indicates that more work needs to be done to confirm and understand the reasons for these discrepancies and the extent to which they occur. However, when our findings are examined in the context of existing work of others, they suggest that women may require additional, or more intensive, rehabilitation programs following periods of immobilization or bed rest."

Source: American Physiological Society