Don’t Be A Lazy Bone!

Research shows that there are lifelong benefits of youth participation in sports on bone size and strength, published in PNAS this month by a group of scientists from the U.S. and Australia.  The researchers studied the bone properties of major league and minor league baseball players throughout their careers.

Previous studies have shown that physical activity during youth is beneficial for bone mass, but that these benefits are lost after the physical activity is ceased.  However, this study showed that increases in bone size, measured by cross-sectional area, and bone strength, measured using the physics of torsional rigidity are maintained throughout adulthood.  Physical activity during youth increases new bone on the outer periosteal surface of the bone to increase bone size, whereas aging related bone loss occurs on the endocortical surface.  Therefore, increased bone size acquired through physical exercise isn’t as impacted by the normal process of aging because these two processes affect different areas of the bone.

Reconstructed CT images showing a larger diameter of the throwing arm compared to the nonthrowing arm in major league baseball players.

Reconstructed CT images showing a larger diameter of the throwing arm compared to the nonthrowing arm in major league baseball players.

In this experiment, researchers compared the throwing-to-nonthrowing arm differences of the major and minor league baseball players, compared to dominant and nondominant arms in control individuals, who did not participate in physical activity to the degree that the baseball players did.  Throwing-related physical activity, which is modeled by movements performed in baseball, cause extreme loading on the bones.  Bones have the ability to adapt to elevated mechanical loading, and thus this increases the strength of the bones involved in the movement.  However, there is more plasticity, or ability to change, in response to increased mechanical load during youth than in adulthood.  For this reason, it is important for participation in physical activity to occur in youth rather than adulthood.

Furthermore, in players who continued to throw after finishing their baseball career, some of the bone mass and strength benefits of the physical activity they participated in as youth was maintained more than individuals who didn’t continue throwing after the end of their career.  Thus, the results of this study show that physical activity during youth can have lifelong effects on bone strength and size, even if activity ceases during adulthood.

To view full article:

Warden, S. J., Roosa, S. M. M., Kersh, M. E., Hurd, A. L., Fleisig, G. S., Pandy, M. G., & Fuchs, R. K. (2014). Physical activity when young provides lifelong benefits to cortical bone size and strength in men. Proceedings of the National Academy of Sciences, 201321605.

About Lydia Marks