The Association Between Muscle Power Measured During A Novel Sit-To-Stand Power Test And Bone Density

INTRODUCTION: There is already evidence that bodyweight and resistance training exercises increase bone mineral density (BMD) and muscle power (POW). BMD and POW are especially important to our aging population since POW is strongly associated with the risk of falls and low BMD increases the risk of fractures. Whether there is an association between POW and BMD remains elusive. PURPOSE: The purpose of this study was to examine the association between POW and BMD, in a sample of middle-aged and aging adults. METHODS: 40 volunteers, 40+ years of age (mean age = 58.0 years; 70% female), participated in this cross-sectional study. Mean body-mass normalized POW was estimated, using a linear position transducer (LPT) during 5 maximal-velocity sit-to-stand maneuvers, with 1-min. rest between attempts. BMD was obtained with a DXA scan, and osteopenia/osteoporosis (OSTEO) was defined as having a whole-body BMD T-score ≤ -1.0. The mean difference in POW between those with and without OSTEO was assessed with a two-tailed, two samples t-test. A multiple logistic regression model was used to assess the relationship between BMD and POW, while controlling for age, sex, and BMI, with coefficients and their 95% confidence intervals reported. An alpha value of 0.05 was used for all analysis. RESULTS: Those with OSTEO (n = 11, 28%) had significantly lower mean POW, compared to those without (5.01 vs. 6.18 W/kg, respectively; g = 0.77). In multiple logistic regression analyses, one-unit increase in mean STS POW was associated with a 78% [21, 92%] lower risk of OSTEO (OR = 0.32 [0.08, 0.79], p = 0.04). CONCLUSIONS: Participants with OSTEO did have a lower POW output when compared to those without. Although associations were found to exist irrespective of age, sex, and BMI, further study with a larger, more diverse sample is needed. For those at risk of OSTEO, power focused resistance training programs may be beneficial.