Physical activity completed when young has residual bone benefits at 94 years of age: a within-subject controlled case study.

Physical activity is recommended for skeletal health because bones adapt to mechanical loading. The young skeleton shows greatest plasticity to physical activity-related mechanical loads, but bones are most at risk of failure later in life. The discrepancy raises the question of whether the skeletal benefits of physical activity completed when young persist with aging. Here we present a unique case wherein the cortical bone benefit of physical activity completed over five decades earlier could be established within an individual aged in their tenth decade of life. Specifically, we compared bone properties at the midshaft humerus between the throwing and nonthrowing arms of a 94-year-old former Major League Baseball player who ceased throwing 55 years earlier. By performing analyses within-subject, the long-term skeletal benefit of physical activity completed when young could be assessed independent of inherited and systemic traits. Also, as the subject threw left-handed during his throwing career, but was right-hand dominant in all other activities throughout life, any lasting skeletal benefits in favor of the throwing arm could not be attributable to simple arm dominance. Analyses indicated that any cortical bone mass, area and thickness benefits of throwing-related physical activity completed when young were lost with aging, possibly due to accelerated intracortical remodeling. In contrast, the subject's throwing (nondominant) arm had greater total cross-sectional area and estimated strength (polar moment of inertia) than in his dominant arm, despite muscle indices favoring the latter. These data indicate that physical activity completed when young can have lasting benefits on bone size and strength, independent of the maintenance of bone mass benefits.

Age-related changes in proximal humerus bone health in healthy, white males.

UNLABELLED: The proximal humerus is a common site for osteoporotic fracture. The current study demonstrates the rate of age-related decline in proximal humerus bone health. The data suggest aging is associated with considerable loss of bone mass, structural deterioration and reduced bone strength at the proximal humerus. INTRODUCTION: The proximal humerus is relatively under investigated despite being the fourth most common site for osteoporotic fracture. METHODS: A cross-sectional study was performed to assess age-related changes in dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) properties of the proximal humerus in a cohort of 170 healthy, white males. RESULTS: Regression models estimated considerable age-related loss of DXA measured bone quantity at the proximal humerus, with areal bone mineral density modeled to decline by 29% (95% confidence interval [CI], 17.5-35.0%) in the 50 years between ages 30 and 80 years (p < 0.001). pQCT measures indicated aging was associated with progressive periosteal and endosteal expansion, with the later occurring more rapidly as indicated by age-related declines in cortical bone mass, area and thickness (all p < 0.01). The net result of the density, mass and structural changes was a 26% (95% CI, 13.5-38.0%) decline in pQCT estimated proximal humerus bone strength in the 50 years between ages 30 and 80 years (p < 0.001). CONCLUSION: Aging is associated with considerable declines in proximal humeral bone health which, when coupled with a traumatic event such as a fall, may contribute to osteoporotic fracture at this site.