Impact of Body Weight on Postural Sway in Women

Abstract

INTRODUCTION: Body weight and weight distribution impact body inertia, center of gravity, and postural stability. Many studies indicate that obesity and a variety of chronic diseases that involve weight gain are associated with postural instability. However, there is a lack of research examining the relationship between Body Mass Index (BMI) and weight distribution on postural stability in women. PURPOSE: The purpose was to identify differences in postural sway based on BMI and to determine if addition of appended weight would result changes in postural stability. It was predicted that addition of 10 lbs anteriorly would have a negative impact on balance and that overweight (OW) women (BMI = 25) would have poorer balance than women with normal weight (NW) (BMI< 25). METHODS: Forty nine (49) females 18-60 yo (26.9"12.2) participated. Testing involved four tests performed on the NeuroCom Balance Master®: the modified Clinical Test of Sensory Interaction on Balance (SIB), Unilateral Stance (US), Sit-to-Stand (STS), and Step/Quick Turn (SQT). Two of the tests (SIB and US) evaluate sway with eyes open (EO) and closed (EC) and the SIB is performed standing on a foam block. Tests were performed once and then repeated with the addition of a 10 lb backpack worn anteriorly to simulate added centripetal fat. Measures of sway velocity (SV) were used to assess postural stability. RESULTS: Paired-t tests were used to evaluate differences in sway pre-and post-weight addition. Significant (p<.05) differences existed from pre-to post-weight for SIB-EO, SIBEC, STS, and SQT, with SV decreasing (improved balance) with the addition of weight. Independent t-tests were used to compare SV for NW vs OW women. Significant differences in SV existed based on weight status for SIB-EC without weight, SIB-EC with weight, STS without weight, US-EO with weight, and US-EC with weight. The OW women had less sway on both SIB measures and the NW had less sway on the US measures. CONCLUSIONS: Pre-to post-weight differences may have resulted from a beneficial effect of extra weight in stabilizing the body or may reflect a practice effect when the tests were repeated with weight. The NW to OW comparison suggests that added weight may stabilize on a conforming surface like foam while it is detrimental to maintaining balance with a restricted base of support (one leg).