Exercise during youth builds strong bones for life
Tuesday, 25 March 2014
A study of major league baseball players’ pitching arms has shown that bone strength in later life is decided by the quality of exercises we do in our youth.
The research by US and Australian scientists is published today in Proceedings of the National Academy of Sciences throws a curveball at the concept of ‘use it, or lose it’ in the context of bone health.
Researchers examined the cross-sectional size of the humerus — the upper arm bone — it’s torsional strength, bone mass and bone mineral density of the throwing arms of 103 professional baseball players at various stages of their careers.
They found that even decades after players had stopped playing baseball, the cross-sectional size of the bone — which is a key determinant of bone strength — was largely preserved.
“The current paradigm seems to be that if you increase bone mass then you preserve bone strength over a lifetime, but we know that as we age the bone mass decreases,” says research Professor Marcus Pandy, chair of biomedical and mechanical engineering at the University of Melbourne.
“What we found was is that in these baseball players, whether they continued to pitch or not, bone mass did decrease, but the size of their bones did not decrease.”
Baseball players were used in the research because when they throw a fast ball, the muscles in the upper part of the arm twist and therefore twist the bone.
The CT imaging used in the study showed that over time, that twisting motion causes the outer surface of the bone to increase in size.
Bone size v bone mass
The findings have implications for current advice on how to preserve bone strength throughout life, suggesting that it’s more important to focus on activities that increase bone size such as strength training.
“It says that the things that you do when you’re young have lasting effects, so the common adage of ‘use it or lose it’ may not apply to the skeleton,” Pandy says.
“We think it applies to muscle, but in terms of the skeleton if you do the right types of exercise and strain the bones in the right way and grow bone size when you’re young, the total area of the bone is preserved and therefore the torsional strength of the bone is preserved.”
Researchers were also able to compare bone size and strength in players who had continued to play baseball even after finishing their professional careers with those who had gone ‘cold turkey’ once their careers were over.
They found that even former players in their nineties, who hadn’t thrown a ball in fifty years, still retained more than half of the throwing-related increase in bone size — around the same amount as those who continued playing — and around one-third of the benefits in bone torsional strength.
Players who continued to throw kept the same amount of bone size, but also preserved more of the bone strength.
“The bone gets less dense and therefore it loses mass, but if you can preserve the size of the bone then you preserve the strength,” Pandy says.