Adaptive responses of aging bone to physical exercise : masters athletes and patients with hip fracture as a research model

Abstract

Physical function and physical loading, especially intensive osteogenic exercise, typically decrease with age, a phenomenon which likely contributes to age-related bone loss and a reduction in the osteogenic potential of exercise during aging. This study examined osteogenic responses to specific exercise among older adults representing the opposite ends of the physical function and bone health spectrum. Competitive male masters athletes aged 40-85 years participated in a randomized, controlled 20-week high-intensity strength and sprint training intervention (n=72) and in a 10-year follow-up (n=69). Men and women over age 60 years with a recent hip fracture (n=81) participated in a 12-month randomized controlled home-rehabilitation program. Tibial bone properties were assessed with peripheral quantitative computed tomography (pQCT). Physical function was measured with the Short Physical Performance Battery (SPPB) and perceived difficulty in walking outdoors, and lean body mass (LBM) was measured with a bioimpedance device. Compared to the athletes maintaining their usual sprint training schedules, the 20-week intensified strength and sprint training program improved the mid-tibial cross-sectional geometry and strength of the athletes in the intervention group. Strength and sprint training continued over 10 years was associated with maintained distal tibia bone mass, density and strength, and improved mid-tibia bone mass and geometry. In the less-trained athletes, who had reduced their training load, the corresponding bone properties declined during the follow-up. The home-based rehabilitation program had no effect on the tibial bone properties of the older adults with hip fracture as compared to those receiving standard care. Lower physical function and lower LBM were, however, predictive of greater deterioration in distal tibia bone traits during the first year post fracture. This research suggests that regular high-intensity exercise maintains the ability of a healthy aging bone structure to adapt to increased loading and counteracts age-related loss in bone cross-sectional geometry, density and strength. In aging people, a sufficient level of muscular capacity and physical function seem to be essential for bone maintenance across the physical activity and bone health spectrum.