Stability on the move: Investigating the effects of speed and path width on stability control mechanisms during walking

• Ahmed Alkaye, Exercise Science, University of Delaware

• Jeremy Crenshaw, KAAP, University of Delaware

Side-to-side or frontal plane balance must be actively controlled during walking. We control balance in our frontal plane through two mechanisms: foot placement and push-off. Foot placement is the positioning of the foot lateral to the whole-body center of mass. Push-off mechanisms are forces generated by the trailing foot that limit lateral acceleration. Both mechanisms contribute to balance and proper movement. Step width and walking speeds should directly influence the relative step location and the magnitude of forces experienced during stepping and therefore will influence our proposed walking-stability-control mechanisms. The purpose of this study was to explore the extent to which walking speed and step width impact our novel stability-control measures. We developed a biomechanical method to quantify push-off and foot placement contributions to stability during walking. We recruited four participants with no neuromuscular impairment. Participants were outfitted with a full-body motion-capture marker set and walked on a force-plate instrumented, dual-belt treadmill. Participants walked under four conditions: slow speed, preferred speed, fast speed, and with a narrow step width. We anticipate that larger ground reaction forces will result in increased push-off and foot-placement contributions to stability control at faster walking speeds. Conversely, we predict that these contributions will be reduced with narrower steps due to forces being placed closer to the center of mass. The basic knowledge generated from this study will inform hypotheses for future applied studies of those with impaired walking balance, such as older adults and people with stroke.