Contraceptives and muscle gains.

NEW ORLEANS -- Some female athletes may pay a price for using oral contraception: lower strength gains from resistance exercises, which include lifting weights or working against tension bands and bars.

Personal trainers have long noted that all women don't garner the same benefits from such exercise, and Chang Woock Lee of Texas A&M University in College Station and his colleagues wanted to know why.

After 10 weeks of intense resistance training, women taking oral contraceptives gained an average of 2.1 percent muscle mass--compared with 3.5 percent in women not on the pill, Lee reported April 21 at the Experimental Biology 2009 meeting. And before and after the trial, women on the pill had dramatically lower blood levels of natural muscle-building hormones and substantially higher concentrations of cortisol, a hormone associated with the breakdown of muscle, than did recruits not on the pill.