Lower limb muscle strength is associated with poor balance in middle-aged women: linear and nonlinear analyses. Issue 7 (July 2016)

• Record Type: Journal Article
• Authors: Wu, F.; Callisaya, M.; Laslett, L.; Wills, K.; Zhou, Y.; Jones, G.; Winzenberg, T.
• Is Part Of: Osteoporosis international. Volume 27:Issue 7(2016)
• Page Start: 2241
• Page End: 2248
• Publication Date: 2016-07
• Subjects: Balance -- Middle-aged women -- Muscle strength; Osteoporosis -- Periodicals; Bones -- Metabolism -- Disorders -- Periodicals; 616.716005
• DOI: 10.1007/s00198-016-3545-3
• Languages: English
• ISSNs: 0937-941X

Abstract

Abstract Summary This was the first study investigating both linear associations between lower limb muscle strength and balance in middle-aged women and the potential for thresholds for the associations. There was strong evidence that even in middle-aged women, poorer LMS was associated with reduced balance. However, no evidence was found for thresholds. Introduction Decline in balance begins in middle age, yet, the role of muscle strength in balance is rarely examined in this age group. We aimed to determine the association between lower limb muscle strength (LMS) and balance in middle-aged women and investigate whether cut-points of LMS exist that might identify women at risk of poorer balance. Methods Cross-sectional analysis of 345 women aged 36–57 years was done. Associations between LMS and balance tests (timed up and go (TUG), step test (ST), functional reach test (FRT), and lateral reach test (LRT)) were assessed using linear regression. Nonlinear associations were explored using locally weighted regression smoothing (LOWESS) and potential cut-points identified using nonlinear least-squares estimation. Segmented regression was used to estimate associations above and below the identified cut-points. Results Weaker LMS was associated with poorer performance on the TUG (β −0.008 (95 % CI: −0.010, −0.005) second/kg), ST (β 0.031 (0.011, 0.051) step/kg), FRT (β 0.071 (0.047, 0.096) cm/kg), and LRT (β 0.028 (0.011, 0.044) cm/kg), independent of confounders. Potential nonlinear associations were evident from LOWESS results; significant cut-points of LMS were identified for all balance tests (29–50 kg). However, excepting ST, cut-points did not persist after excluding potentially influential data points. Conclusions In middle-aged women, poorer LMS is associated with reduced balance. Therefore, improving muscle strength in middle-age may be a useful strategy to improve balance and reduce falls risk in later life. Middle-aged women with low muscle strength may be an effective target group for future randomized controlled trials. Trial registration Australian New Zealand Clinical Trials Registry (ANZCTR) NCT00273260.