Most men are not aware that they are at risk for osteoporosis. And those that are may believe that resistance training alone will protect them from the decreasing bone-density that can lead to injury in older age. A new study indicates that high-impact exercise—think running—may have more benefits than, say, the bench press when it comes to increasing bone mineral density. And before you blow this off as a woman's problem think about this: this study was conducted entirely on men.
The study, conducted by researchers at the University of Missouri, took measures of 42 athletes between the ages of 19 and 45. One group were cyclists, another runners, and a third weight-lifters. Measurements of the bone mineral density (BMD) of all three groups were taken, as well as calculations of lean muscle and fat. The results, published this month in the Journal of Strength and Conditioning, threaten to overturn, or at least substantially amend, conventional wisdom about the best preventive exercise for osteoporosis. Currently, doctors recommend weight-bearing or resistance exercise to increase BMD. But the Missouri study found that runners had the highest BMD of all, once lean body mass was taken into account.
Lean body mass is the sum of all the parts of your body not made of fat—muscle, bone, organs, blood, even water. Resistance training athletes, as you might expect, have significantly higher lean body mass than other kinds of athletes, because they have so much muscle. One might predict that this greater muscle mass leads to higher bone mineral density. And, in fact, if this fact was not adjusted for, the resistance training group had the greatest BMD—but if lean body mass was taken into account, runners suddenly had, as the researchers put it, "significantly greater spine BMD". In fact, it appears that high impact exercise like running may, as the researchers put it, "override the benefits of lean body mass on BMD." As Dr. Pam Hinton of Missouri University's College of Human Environmental Sciences, a lead author on the study, explained to the press, "The results of the study confirm that both resistance training and high-impact endurance activities increase bone mineral density. However, high-impact sports, like running, appear to have a greater beneficial effect."
That was all pretty deep in the scientific weeds. Here's how Dr. Hinton breaks it down for the layman: "Exercise programs to increase bone strength should be designed using what is known about how bones respond to exercise. Only the skeletal sites that experience increased stress from exercise will become stronger. For example, performing upper body resistance exercises will not increase bone mineral density of the hips. The response of bone to loading is determined by the magnitude of the force, and the rate and direction(s) at which it is applied. Therefore, high-impact, dynamic, multi-directional activities, including structured jump-training (plyometrics), result in greater gains in bone strength. Playing basketball, volleyball, or soccer are also good options."
In other words, if you are doing all non-weight-bearing exercises, you could help yourself just by increasing your lean body mass—by being more like a weight-lifter. But if you are engaged entirely in non-impact exercise—even those previously recommended for osteoporosis, such as swimming—you could help yourself with a bit of running.
Why should you care? Though bone density will always decrease with age, if that loss becomes intense or goes untreated, even small incidents can result in potentially crippling bone-breaks. And the statistics on osteoporosis in men are enough to give one pause, despite the fact that many men dismiss this as a woman's disease. It is true that osteoporosis is more common in women, because it is associated with smaller, weaker bones, which are more commonly found in women. But even so, two million American men currently suffer from osteoporosis, with an additional 12 million at risk for the disease. And, osteoporosis is under-diagnosed in men, precisely because of the common assumption that it will only be a problem for women. Who is at risk? Men who have had prolonged exposure to certain drugs (steroids, anticonvulsants, some cancer treatments, some antacids); men with chronically low testosterone; men who smoke, abuse alcohol, or have insufficient calcium intake; men who do not exercise. If any of these risk factors apply to you, you may want to do more than take up running in addition to weight-training—you should probably also talk to your physician about a long-term plan for preserving your bone mineral density.