Increased Trunk Extension Endurance Is Associated With Meaningful Improvement in Balance Among Older Adults With Mobility Problems

Sun P, Kiely DK, Leveille SG, Frontera WR, Bean JF. Increased trunk extension endurance is associated with meaningful improvement in balance among older adults with mobility problems. Arch Phys Med Rehabil 2011;92: 1038-43. Objective: To determine whether trunk extension endurance changes with training are associated with clinically meaningful improvements in balance among mobility-limited older adults. Design: Longitudinal data from a randomized controlled trial. Setting: Outpatient rehabilitation research center. Participants: Community-dwelling older adults (N=64; mean age, 75.9y) with mobility limitations as defined by a score of 4 to 10 on the Short Physical Performance Battery. Interventions: Sixteen weeks of progressive resistance training. Main Outcome Measures: Outcomes were the Berg Balance Scale (BBS) and the Unipedal Stance Time (UST). Predictors included leg strength, leg power, trunk extension endurance, and the product of heart rate and blood pressure (RPP) at the final stage of an exercise tolerance test. We performed an analysis of data from participants who completed 16 weeks of training by using binary outcomes defined by a clinically meaningful change (CMC) from baseline to completion of the intervention (BBS=4 units; UST=5s). The association of predictor variables with balance outcomes was examined separately and together in multivariate adjusted logistic regression models. Results: Trunk extension endurance in seconds (1.04 [1.00-1.09]) was independently associated with CMC on the BBS. Trunk extension endurance (1.02 [1.00-1.03]) was independently associated with CMC on the UST. Other physical attributes were not associated with meaningful change in balance. Conclusions: Improvements in trunk extension endurance were independently associated with CMCs in balance in older adults. Leg strength, leg power, and RPP were not associated with CMC in balance. Poor trunk extension endurance may be a rehabilitative impairment worthy of further study as a modifiable factor linked to balance among older adults.