Researchers at the University of Arkansas made the backyard/gym connection when they looked at the activities—and the bone densities—of more than 3,000 women 50 and older. Strength training (practiced by 45 of the women) and yard work (practiced by 1304) were the only two physical activities highly correlated with strong bones, beating out walking, jogging, swimming, bicycling, calisthenics, and other exercises.

Why? Think of the moves involved in heavy-duty gardening, comments lead researcher [on Turner, PhD, RD. When you haul topsoil, you have to squat to get it, strengthening your quadriceps (muscles in the front of your upper leg) in the process. Carrying a big bag of soil is akin to doing biceps curls, working the tops of your arms. Digging with a shovel uses your shoulder muscles, and pushing a mower works your triceps—the muscles at the back of your upper arms. In other wards, intense yard work is a form of strength training. Dr. Turner points out in her study that the kind of yard work she’s talking about "is not a dainty activity’ like watering the window boxes. It requires "elbow grease" for things like pushing wheel barrows, pulling weeds, digging holes, and edging flower beds. But, she adds, it’s elbow grease people might be willing to use. "For a sedentary person, the word ‘exercise’ can be a turnoff," she says. It sounds tiring and boring. "But gardening isn’t thought of as exercise," so it could be a way of getting an inactive person going. That’s because "regardless of how rigorous" the gardening is, Dr. Turner remarks, "people like it. They enjoy making their yard look beautiful" And that, in turn, can keep them sticking with the activity, both short-term and long-term.

Dr. Turner, who is 44 herself and thinking about protecting her bones for later years, says that "when I’m working in the yard, I’ll go outside to pull a few weeds, but then I see something over here and something over there, and before I know it an hour or two has gone by. It’s not like my workout routine, where I’m watching the clock. The time passes quickly’ It’s a point worth keeping in mind now that in most parts of the country, it’s just about time to haul away dead brush, re-edge the flower beds, carry and put down large bags of mulch, and start mowing again.