FRIDAY, April 17 (HealthDay News) -- Active young women who take oral contraceptives develop less muscle than their counterparts not using the pill, possibly due to differences in hormone levels, according to a study to be presented at the 122nd Annual Meeting of the American Physiological Society, part of the Experimental Biology 2009 scientific conference held from April 18 to 22 in New Orleans.
Chang-Woock Lee, of Texas A&M University in College Station, and colleagues conducted a study of 73 women aged 18 to 31 years, of whom 34 were taking oral contraceptives and 39 were not. The women engaged in a 10-week program of resistance exercise training. Body composition and levels of dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), cortisol, and insulin-like growth factor-I (IGF-1) were measured before and after the training program.
Women in the oral contraceptive group gained less lean mass after the exercise program and had significantly lower plasma levels of DHEA, DHEAS and IGF-1, as well as elevated levels of cortisol, the investigators discovered.
"The diminished lean mass gain may be related to the androgenicity of progestin which may bind to androgen receptor and inhibit its function," the authors write. "We were surprised at the magnitude of differences in muscle gains between the two groups, with the non-oral contraceptive women gaining more than 60 percent greater muscle mass than their oral contraceptive counterparts," they added in a statement.
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