A new look at an old problem: Defining weight acceptance in human walking

Background: Weight acceptance (WA) is an important phase of bipedal gait that has received relatively little study to date. This study tested the hypothesis that the first peak knee flexion would better demarcate the end of WA power absorption activity across varying gait speeds than would the more commonly used event of contralateral toe off (CTO) or the peak hip adduction angle. Methods: Eight control subjects (4F/4M) walked on a treadmill at slow, self-selected, and fast speeds. Kinematic and kinetic data were recorded. Joint angles and power absorption were analyzed about the, lower extremity joints (sagittal ankle, knee, hip and frontal hip). Differences in event timings and, magnitudes of negative work were analyzed (ANOVA). Results: Knee sagittal power absorption continued after the CTO event at self-selected (p = 0.009) and fast speeds (p = 0.001), while hip frontal power absorption continued after the CTO event at slow (p = 0.019), self-selected (p = 0.001), and fast speeds (p = 0.001). The contribution of frontal hip to overall power absorption increased as speed decreased. Discussion: Peak hip adduction angle is the best kinematic marker of the end of the WA phase, and peak knee flexion angle is the best alternative marker across speeds. CTO is only appropriate to use when gait speeds are slow. In addition, the relative contribution of power absorbed in the frontal hip during WA highlights the importance of frontal plane pelvic control in locomotion, especially when gait speed is slow. (C) 2013 Elsevier B. V. All rights reserved.