Relative effects of weight loss and strength training on balance recovery.
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.


OBJECTIVE
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 x 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, thetamax, 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 thetamax.


RESULTS
Both strength training and weight loss increased thetamax. Comparing the percent changes in weight and strength required to increase thetamax, a targeted amount revealed differences in intervention potency. For example, to increase thetamax by 1 degree, 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 thetamax 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.
Matrangola
Sara L
SL
Virginia Tech-Wake Forest School of Biomedical Engineering and Sciences, Blacksburg, VA, USA.
Madigan
Michael L
ML
D000058:Accidental Falls / Q000517:prevention & control* / Q000706:statistics & numerical data; D000328:Adult; D000704:Analysis of Variance; D000842:Ankle / Q000502:physiology; D015992:Body Mass Index; D004576:Electromyography; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D009765:Obesity / Q000150:complications*; D004856:Postural Balance; D012307:Risk Factors; D019415:Torque; D014768:Virginia / Q000453:epidemiology; D015431:Weight Loss