title: Ankle torque control that shifts the center of pressure from heel to toe contributes non-zero sagittal plane angular momentum during human walking.
abstract: A principle objective of human walking is controlling angular motion of the body as a whole to remain upright. The force of the ground on each foot (F) reflects that control, and recent studies show that in the sagittal plane F exhibits a specific coordination between F direction and center-of-pressure (CP) that is conducive to remaining upright. Typical walking involves the CP shifting relative to the body due to two factors: posterior motion of the foot with respect to the hip (stepping) and motion of the CP relative to the foot (foot roll-over). Recent research has also shown how adjusting ankle torque alone to shift CP relative to the foot systematically alters the direction of F, and thus, could play a key role in upright posture and the F measured during walking. This study explores how the CP shifts due to stepping and foot roll-over contribute to the observed F and its role in maintaining upright posture. Experimental walking kinetics and kinematics were combined with a mechanical model of the human to show that variation in F that was not attributable to foot roll-over had systematic correlation between direction and CP that could be described by an intersection point located near the center-of-mass. The findings characterize a component of walking motor control, describe how typical foot roll-over contributes to postural control, and provide a rationale for the increased fall risk observed in individuals with atypical ankle muscle function.
authors: Department of Kinesiology, University of Wisconsin, Madison, WI, United States; Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53706, United States. Electronic address: kggruben@wisc.edu.
authors: Kreg G
authors: KG
authors: Gruben
authors: Department of Kinesiology, University of Wisconsin, Madison, WI, United States; Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53706, United States.
authors: Wendy L
authors: WL
authors: Boehm
mesh_terms: D000328:Adult; D000842:Ankle / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena; D005260:Female; D005528:Foot / Q000502:physiology*; D005684:Gait; D006365:Heel / Q000502:physiology*; D006615:Hip / Q000502:physiology; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D011187:Posture / Q000502:physiology; D011312:Pressure; D014034:Toes / Q000502:physiology*; D019415:Torque; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Balance; Center of mass; Gait; Ground reaction force; Upright posture