Exercise when young makes bones stronger for life

Bone is a living tissue that gets stronger in response to the forces associated with exercise. Exercise has the greatest benefit on bone strength during growth; but until now whether the benefits of exercise during youth persist with ageing, was largely unknown.

A series of studies published in the Proceedings of the National Academy of Sciences looked at differences between the throwing and non-throwing arms of baseball players at different stages of their career and compared them to non-baseball players.

The research team involved found that half of the bone size and one-third of the bone strength benefits of exercise performed during youth were maintained throughout life.

“This is an impressive level of maintenance, particularly considering that the baseball players had not thrown, or in other words, exercised, in over 50 years and were aged in their mid-80s,” Dr Stuart Warden says.

But the amount of new bone added via exercise during youth was progressively and ultimately lost during ageing, ie exercise during youth has a lifelong benefit on bone strength, but not mass.

“While we have historically been encouraged to exercise during youth to put ‘more bone in the bank’ to lose during aging, it is not energy efficient for the skeleton to maintain its mass in excess of its needs,” Dr Warden says.

“Exercise during youth adds extra layers to the outer surface of a bone to essentially make the bone bigger. This gives you more ‘bang for the buck,’ as the addition of a small amount of new material to the outside of a bone results in a disproportionate increase in bone strength relative to the gain in mass.”

As bone loss during aging primarily occurs on the inside rather than outside of a bone, Dr Warden noted that the bigger and consequent stronger bone created by exercise during youth has a means of lasting lifelong.

The team then tested retired baseball players; some had stopped throwing balls when their careers were over but others had continued to throw for 20 years. Those who continued to throw during ageing did not have bigger bones, but the loss of bone material from the inside was prevented.

“The net result was the maintenance of even more of the strength benefit of exercise completed during youth, with baseball players who continued to throw during aging maintaining over 50% percent of the bone strength benefit of exercise performed in youth,” Dr Warden says.

Moving forward, exercise should be strongly promoted during growth to promote lifelong bone health. And exercise should be continued as we age to maintain as much of the benefits of exercise generated during youth, as well as to maintain muscle strength, balance and reduce fall risk.