There are long-term benefits of physical activity to bone size and strength, according to a study of baseball players in the US.
Physical exercise may promote increases in bone mass, size, and strength that are retained to some degree throughout life, and these increases may be retained longer in those who continue to exercise as they age.
Stuart J. Warden and colleagues compared mass, size, and strength in the throwing and non-throwing arms of 103 professional baseball players during their careers and after retirement.
Working baseball players displayed greater humerus mass, size, and strength in their throwing arms than in their non-throwing arms, with bone strength twice as high in the throwing arm.
After retirement, players who stopped throwing eventually lost all of the bone mass benefits in their throwing arms as they aged.
In contrast, retired players who remained active retained 28% of the bone mass benefit.
Inactive players in their 80s retained 56% of the bone size and 34% of the bone strength benefits in their throwing arms that they had built when young, despite not throwing for more than 50 years.
Bone strength benefit retention in active retirees rose to 50%. According to the authors, the results suggest that exercise at a young age increases bone mass, size, and strength, and that the improved bone size and strength are retained well into late adulthood, despite lack of exercise.
The study is published today in PNAS (Proceedings of the NAtional Academy of Sciences).
reveal a bigger bone in the throwing arm than on the non-throwing arm when the bone is
viewed from the front (left images). Cross-sectional images (right) displayed greater total and cortical bone areas, greater cortical thickness, and smaller medullary area in the throwing arm
than in the non-throwing arm. The net result was a stronger bone in the throwing arm, with
one-third of the bone strength benefit lasting lifelong in retired players despite throwing
being completed more than 50 years earlier.
Image: Stuart Warden.
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