Muscle Strength and Bone Strength Assessed with Osteo-sono Assessment Index Among Recreationally Athletic Japanese Women

Abstract

Low muscle strength is an independent risk factor for low bone strength, which is a well-established predictor of osteoporotic fracture. However, the association between muscle strength and bone strength remains unclear among recreationally athletic Asian women. PURPOSE: To investigate the association between muscle strength and bone strength among recreationally athletic Japanese women. METHODS: This cross-sectional study was conducted in 7091 recreationally athletic Japanese women [mean (standard deviation), age 50.3 (15.2) years] who had undergone medical checkup and various exercise tests voluntarily from 1998 to 2016 at a preventive medical center. Participants completed a maximal voluntary knee extension test, quantitative ultrasound (QUS), calcaneal measurements, a medical examination, and questionnaires on lifestyle. Muscle strength, expressed as Nm per body weight in kilogram (Nm/kg), was measured at 60 degrees/s in the knee with an isokinetic dynamometer. The osteo-sono assessment index (OSI) evaluated right calcaneus heel bone strength using a QUS measurement. Multiple linear regression analysis assessed independent association of muscle strength and OSI (×106) after adjustment for age, systolic blood pressure, smoking, drinking, prevalence of diabetes, and body mass index. RESULTS: Muscle strength had a positive association with OSI score after adjustment for potential confounding factors (β=0.17, 95% confidence interval; 0.15-0.19, p <0.001). Furthermore, age-stratified (≥50 years and under) analyses showed similar patterns of association. CONCLUSIONS: Our results suggest a dose-response association between muscle strength and bone strength after adjustment for potential confounding factors. We need to further investigate longitudinal relationship between muscle strength and bone strength in a cohort study.