It is well known that athletes tend to have greater bone mineral density (BMD) than couch potatoes, as well as better muscle mass and strength. That’s why exercise is recommended to combat the loss of bone mass that can lead to osteoporosis. Other factors–especially genetics, hormones, and nutrition–also contribute to bone mineral density. But exercise can play a vital role in helping people build and maintain strong bones.
But which type of exercise is best for building bone? Medical professionals and researchers aren’t exactly sure how or why exercise stimulates bone building. It is known that weightbearing activities, such as aerobics classes and weight lifting, are better at increasing BMD than nonweightbearing exercise, such as swimming or bicycling. Recent studies have also suggested that runners tend to have lower BMD.
These researchers studied four groups of young men to measure how different kinds of exercise affect BMD and muscle mass in the arms and legs. Three of the groups consisted of highly competitive athletes. One group was made up of judo athletes, one of karate, and one of water polo players. All athletes exercised at least three hours a day, six days a week. The control group was made up of nonathletes. Researchers measured all the men’s BMD and muscle mass using special X-ray technology.
As expected, all the athletes had significantly higher BMD and muscle mass than the control group. The judo athletes had higher BMD than the other groups. This supports the idea that weightbearing sports build bone better, because judo is an especially high-intensity weightbearing activity. On the other hand, the water polo players had the highest muscle mass. But their increased muscle mass did not correspond to higher BMD. This supports the idea that muscle building alone does not build stronger bones. It also suggests that nonweightbearing exercises are not as optimal for building bone density as weightbearing ones. The researchers also noted higher BMD in areas of the skeleton that were subjected to higher exercise loads.
This study is far from the last word on weightbearing exercise and BMD. The authors note that many factors may have influenced BMD on this small group of athletes, including physical activity as a child, amount of different minerals and vitamins in the diet, and metabolism. They suggest further research on these and other variables. But based on what we know now, bone health is affected by some activities more than others.