A BMJ review of 124 trials in over 18,000 adults 40 and up finds brisk walking and jogging did the most for bone density.

Here's a study worth reading carefully, especially if you're over 40 and wonder whether your daily walk counts for much. A new study published in The BMJ analyzed the results of 124 existing trials involving more than 18,000 adults aged 40 and over, Women's Health reports, to see how different kinds of exercise affect bone density. The researchers compared six categories: mixed aerobic exercise, resistance training, combined aerobic and resistance training, brisk walking or jogging, mind-body exercise such as tai chi and yoga, and whole-body vibration. Overall, structured exercise was associated with improvements in age-related bone density decline. Brisk walking and jogging came out on top. Combined aerobic and resistance exercise also helped, though its effects showed up in fewer areas of the skeleton. The researchers also estimated how much exercise it takes to produce clinically meaningful benefits: around 600 MET minutes per week, a measure of energy expenditure. In practical terms, they say, that's roughly two to three hours of brisk walking or jogging each week. Their explanation is that brisk walking is weight-bearing and repeatedly loads the skeleton with moderate impact, which helps stimulate bone maintenance. Osteoporosis and related fragility fractures affect more than 200 million people worldwide, the magazine notes. Now the caveats. This is a review that pools earlier trials, and not all of the underlying evidence was of equally high quality; the trials varied considerably in their design. A pooled analysis can show which approaches tended to do best across many studies, but it can't tell you what's right for your own bones, joints or heart. So bring it to your next checkup. Ask whether a bone density scan makes sense for you, whether brisk walking or jogging is safe for your joints and heart, and whether you should add strength training, too.