Associations of muscle strength and functional power with longitudinal change in HR-pQCT bone parameters: the Osteoporotic Fractures in Men (MrOS) Study.

Both bone and muscle function decline with age and are anatomically and functionally related. However, whether and to what extent muscle function (ie, strength and power) may predict longitudinal changes in bone microarchitecture and strength is unclear. The Osteoporotic Fractures in Men (MrOS) Study included assessments of peak jump power (W) from a force plate and maximum grip strength (kg) from a dynamometer, both normalized to body weight at visit 4 (2014-2016). We investigated the associations of jump power and grip strength with annual percent change in volumetric BMD, microarchitecture, and strength at the distal tibia (DT) and radius (DR) from HR-pQCT between visit 4 and visit 5 (2020-2022; 6.2 ± 0.6 yr follow-up; N = 225; age 82.8 ± 3.0 yr; 89% White). Mean jump power was 22.9 ± 5.6 W/kg and grip strength was 0.49 ± 0.1 kg/kg. During follow-up (median [IQR]), failure load (-0.88 [-1.71, -0.31]%), total BMD (-0.57 [-1.12, -0.18]%), cortical BMD (-1.24 [-2.03, -0.67]%), trabecular BMD (-0.05 [-0.47, 0.20]%), and trabecular thickness (-0.37 [-0.64, -0.12]%) declined at the DT, while at the DR, failure load (-1.02 [-2.19, -0.04]%), total BMD (-0.64 [-1.20, -0.18]%), and cortical BMD (-1.38 [-2.15, -0.71]%) declined (all p ≤ .05). Significant increases were observed for total area at both skeletal sites (DT: 0.04 [0.01, 0.08]%; DR: 0.07[-0.06, 0.16]%; both p ≤ .05). Multivariable linear regression models were adjusted for age, White race, clinic site, respective HR-pQCT initial values, percentage weight change, alcohol consumption, medication count, chronic disease history, falls, and hip pain. Higher grip strength was significantly associated with a smaller percent/year increase in total area at the DT (p ≤ .05) but not at the DR. Neither jump power nor grip strength was associated with change in failure load, BMD, or trabecular thickness at either skeletal site. Associations between grip strength and changes in tibial bone geometry provide insight into potential mechanisms for bone loss and targets for musculoskeletal interventions to reduce fracture risk.