Influence of Obesity on Balance Recovery Using an Ankle Strategy

Abstract

Obesity is associated with an increased risk of falls. However, limited research has investigated the influence of obesity on balance recovery after a postural perturbation. This is important because most falls are attributed to some type of postural perturbation. PURPOSE: To determine the effects of obesity on balance recovery from two highly-controlled postural perturbations using an ankle strategy. METHODS: Ten normal weight (mean ± standard deviation, age: 21.3 ± 1.1 years, BMI: 22.7 ± 0.6 kg/m^2) and ten obese (age: 22.4 ± 3.6 years, BMI: 32.2 ± 2.2 kg/m^2) adult male subjects were used in this study. Subjects were instructed to recover balance using an ankle strategy after two types of postural perturbations: release from a static forward lean (which provided an initial angular displacement from the natural standing position and no initial angular velocity), and brief anteriorly-directed force impulses applied at the T6 level of the back (which provided an initial angular velocity from the natural standing position with a negligible initial angular displacement). Balance recovery was quantified by determining the largest initial angular displacement and largest initial angular velocity from which balance could be recovered with an ankle strategy prior to falling too far forward and being caught by a safety rope. A two-way ANOVA was used for to investigate the effects of group (obese vs. normal weight) on these two measures of balance recovery. RESULTS: Obesity did not affect the largest achieved initial angular displacement (obese = 7.18 deg, normal weight = 7.57 deg; p=0.497), but did affect the largest achieved initial angular velocity (obese = 12.76 deg/s, normal weight = 16.53 deg/s; p=0.008). CONCLUSIONS: Obesity impaired balance recovery using an ankle strategy by 29.5% when perturbations were represented as an initial angular velocity, but not when perturbations were represented as an initial angular displacement. These differential effects may provide clues to the specific biomechanical effects of obesity on balance recovery and risk of falls.