Young women can boost their bone strength with just six months of exercise, even if they’ve been sitting on the sidelines for a while.

The key is combining high-impact aerobics and strength training. In a new study, step aerobics delivered the greatest gains in leg, spine, and heel bone density, while hip bones improved more with weight training.

In other words, do some of both types of exercise. While you’re at it, add some weight training exercises to build bones in the upper body. The bone benefits add up quickly, says Michael T.C. Liang of California State Polytechnic University, in a news release.

Aerobics, Weight Training Go Head-to-Head

Exercise amounted to a bone makeover for the women in Liang’s study. Participants were women aged 20-35 years. Like many Americans, they were sedentary, getting basically no exercise.

Liang and colleagues split the women into three groups. One group (29 women) was assigned to do high-impact step aerobics three times a week for six months. Another group (20 women) spent six months on a lower-body strength-training schedule. A third group (20 women) was allowed to stay idle, without any required exercise.

The exercisers got close supervision during their workouts.

At the study’s start and end, the women’s bone density was measured at the heel, leg bones, spine, hip, and wrist. Liang’s team watched to see how bone density changed.

Aerobics Advantage

The step aerobics group had the biggest improvement in heel, spine, and leg strength:

—Hip bone density went up 3.3 percent

—Lumbar spine density went up 1.2 percent

—Leg bone density went up 0.9 percent

The strength-training group did better in the hip area. They had a gain of 0.9 percent in the density of the head of the hip bone, and a tiny hip density increase overall (0.1 percent). Meanwhile, their heel bone density was up 0.1 percent, while leg bone density dropped by 0.4 percent.

Hip density dipped by 0.1 percent and head-of-the-hip density was down 0.7 percent in the aerobics group.

What about the women with no formal exercise program? Their heel bone density dropped 0.2 percent. But their hip and leg bone density each went up by 0.2 percent, says the news release.

The bottom line: Mix high-impact exercise and strength training for best bone results, the study suggests. Strong bones also require adequate calcium, vitamin D, and other nutrients. Those aspects weren’t addressed in this study.

The findings were presented at Experimental Biology 2005, a science conference in San Diego.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Experimental Biology 2005, San Diego, April 2-6, 2005. News release, Federation of American Societies for Experimental Biology.