How does weight-bearing exercise affect bone density?
Dr. Sellmeyer: Physical activity is very important for preventing osteoporosis. The pure bio-mechanical pull of muscle on bone is a stimulus for the bone to grow, incorporate mineral, and become stronger. People who don’t get that stimulus — such as astronauts in space or immobilized people on Earth — start losing bone at a very rapid rate. Ideally, people should perform weight-bearing activities throughout their lives to build bone and maintain bone density. Physical activity makes a big difference, even in childhood. For example, there have been trials in which one group of children was assigned to an exercise program in which they jumped up and down off boxes of varying heights. A second group of children was instructed to simply continue their usual daily activities. The researchers reported that the kids in the exercise group gained significantly more bone than the other kids. That’s because the jumping activity gave them more weight-bearing stress on their bones. It’s never too
