Sensitivity of Dynamic Stability to Changes in Step Width During Treadmill Walking by Young Adults

摘要

Recent experimental findings support theoretical predictions that across walking conditions the motor system chooses foot placement to achieve a constant minimum "margin of stability" (MOS_(min)-distance between the extrapolated center of mass and base of support. For example, while step width varies, similar average MOS(min) exists between overground and treadmill walking and between overground and compliant/irregular surface walking. However, predictions regarding the invariance of MOS_(min) to step-by-step changes in foot placement cannot be verified by average values. The purpose of this study was to determine average changes in, and the sensitivity of MOS_(min) to varying step widths during two walking tasks. Eight young subjects walked on a dual-belt treadmill before and after receiving information that stepping on the physical gap between the belts causes no adverse effects. Information decreased step width by 17% (p - .01), whereas MOS_(min) was unaffected (p = .12). Regardless of information, subject-specific regressions between step-by-step values of step width and MOS_(min) explained, on average, only 5% of the shared variance (β = 0.11 ± 0.05). Thus, MOS_(min) appears to be insensitive to changing step width. Accordingly, during treadmill walking, step width is chosen to maintain MOS_(min). If MOS_(min) remains insensitive to step width across other dynamic tasks, then assessing an individual's stability while performing theses tasks could help describe the health of the motor system.