The gymnasts had highest bone density, and swimmers and cyclists were lowest among athletes. These differences probably result from different weight that is put on the bone during the sports activities. Also, a sudden push or force on the bones is more important than a gradual increase in weight.
For example, when a gymnast dismounts, the bones get a real jolt, about 5 times the gymnast's weight. All the athletes with high bone density do lots of jumping. Swimmers, on the other hand, are floating in the water and their bones don't have to carry much weight. Cyclists and kayakers are sitting and so less weight is on the skeleton.
If weight is important to bones, what happens on the moon? Soon this web site will have a page about Bones in Space!
Just because most athletes have higher bone density than ordinary people does not necessarily mean that the sports increased the bone density. Maybe the athletes had higher bone density to start with. How could you prove whether the exercise itself was improving the bone density and bone strength?
|Obviously everybody can't be an Olympic athlete, but exercise is important to bone strength. Walking and jumping are things almost all kids can do to make their bones strong. Some scientists think that exercise works best in kids who are pre-teens, while the bones are in their growth spurt!|
Click to see evidence that exercise helps bone strength in kids.