Muscle power predicts bone strength in Division II athletes
The relationship between muscle fitness measures and tibial bone strength in collegiate level athletes was investigated. Eighty-six Division II collegiate athletes (age: (18-29 years), height: 1.71 m (.09): mass: 66.7 kg (10.5) 56 female: 30 male) participated in this cross-sectional study. Maximum grip strength (GS), 1 repetition maximum leg press (1RM) and vertical jump peak power (PP) tests were measured. Cortical area (Ct.Ar), cortical bone mineral density (cBMD), moment of inertia (J) and bone strength (polar strength-strain index, SSIp) were measured using peripheral quantitative computed tomography (pQCT) at 50% tibia length. For each bone strength parameter, a hierarchical multiple regression (HMR) analysis was performed to examine the contribution of sex and the 3 muscle fitness parameters (muscle power, relative 1 repetition leg extensor strength and relative grip strength) to bone parameters. Vertical jump peak power explained 54-59% of the variance in bone strength parameters, and relative leg extensor and grip strength were not predictive of bone strength parameters. Muscle power correlated with bone mass and architecture variables but not cBMD values. Cortical bone mineral density (cBMD) was also not predicted by relative leg extensor strength or relative grip strength. Muscular fitness assessment, specifically peak power calculated from vertical jump height assessments provides a simple, objective, valid and reliable measure to identify and monitor bone strength in collegiate athletes.