Atlanta ? Women are pumping more iron, with nearly 1 in 5 doing twice-a-week workouts, a new federal study shows.

The desire for a more attractive body, along with worries about bone loss, probably contribute to the trend, experts said.

The U.S. Centers for Disease Control and Prevention did the research, which is called the first to look at the national prevalence of weightlifting and other forms of strength-training. It is being published this week in the CDC’s Morbidity and Mortality Weekly Report.

Women improved the most: About 17.5 percent did twice-a-week workouts in 2004, up from about 14.5 percent in 1998. Men, in contrast, held steady around 21.5 percent.

Long-term concerns about bone loss and a recognition that strength-training can help also may be factors.