How should the margin of stability during walking be expressed to account for body size?
DOI:
https://doi.org/10.51224/SRXIV.229Keywords:
Dynamic Stability, Walking, Gait, Scaling, BalanceAbstract
Introduction: When expressing the margin of stability (MOS) as a distance, the MOS magnitude has an unclear mechanical interpretation, and it is unknown how body mass and height may influence the measure. In this study, we applied different expressions of the MOS, including that of an impulse, a change in center of mass (COM) velocity, and a scaled, unitless impulse value. The purpose of this study was to determine the influence of body size on these stability margin expressions using walking data from both children and adults. We anticipated that stability margins expressed as an impulse would have strong correlations with body mass and height, as well as large differences between groups. We predicted that scaling for body size would result in weaker correlations and smaller between-group effect sizes. Methods: We calculated each stability margin at the point of minimum lateral values of stance and in the anterior direction at mid-swing. Results: In the anterior direction, the scaled unitless impulse was the only margin to have non-significant relationships with body size (r=-0.10 and -0.08, p>0.05) and small between group effect sizes (d=0.31, p=0.40). In the lateral direction, the MOS, change in velocity margin, and scaled, unitless impulse margin had non-significant correlations (r=-0.20 to 0.17, p>0.05) with body size and small-to-moderate between group differences (d < 0.44, p>0.05). Discussion: We propose using impulse to measure stability margins, as it has has the mechanical implications of the impulse needed to change stability states. If scaling is needed, we encourage using the scaled, unitless impulse.
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Copyright (c) 2022 Nancy T. Nguyen , Michael S. Christensen, James B. Tracy, Grace K. Kellaher, Ryan T. Pohlig, Jeremy R. Crenshaw
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