ABSTRACT: Obesity is associated with an increased risk of falls and injury. Weight loss and strength training can be beneficial to balance, but knowing which is more beneficial would lead to interventions designed for maximal benefit in balance.
Purpose: The goal of this study was to investigate the relative effects of weight loss and strength training on balance recovery using an ankle strategy.
Methods: We used a combination of experimental testing and forward dynamic simulations. Nine male subjects (body mass index = 30.1-36.9 kg·m−2) were released from a forward lean and attempted to recover balance using an ankle strategy. Lean angle was increased until subjects required a step or hip flexion to recover balance. The maximum lean angle, θmax, was used as the measure of balance recovery capability. Experimental data served as inputs to an inverted pendulum model of balance recovery. Multiple simulations were performed to determine the effects of weight and strength on θmax.
Results: Both strength training and weight loss increased θmax. Comparing the percent changes in weight and strength required to increase θmax, a targeted amount revealed differences in intervention potency. For example, to increase θmax by 1°, an 8.6 ± 0.8% decrease in weight or 15.3 ± 1.1% increase in strength was required. The differences in efficacy between the interventions became more apparent as larger increases in θmax were targeted.
Conclusions: Balance recovery can improve with weight loss or strength gain, but a smaller amount of weight loss is needed than strength gain for a targeted improvement in balance recovery. This suggests that weight loss is a more potent intervention than strength training in improving balance recovery using an ankle strategy.
1Virginia Tech-Wake Forest School of Biomedical Engineering and Sciences, Blacksburg, VA; and 2Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA
Submitted for publication September 2008.
Accepted for publication January 2009.
Address for correspondence: Michael L. Madigan, Ph.D., Department of Engineering Science and Mechanics (MC 0219), Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; E-mail: firstname.lastname@example.org.