BIOMECHANICAL ANALYSIS OF BODY-MASS TRANSFER DURING STAIR ASCENT AND DESCENT OF HEALTHY-SUBJECTS

The purposes of this study were to: 1) assess whole body center of mas s (CM) motion in the frontal, sagittal, and transverse planes; 2) comp are CM displacement with center of pressure (CP); and, 3) further defi ne the stance and swing subphases of stair ascent (SA) and stair desce nt (SD) based on critical CM, CP, and ground reaction force (GRF) even ts. SA and SD were analyzed on a convenience sample of 11 subjects. Un paced data were collected from 28 SA trials and 24 SD trials utilizing a bilateral SELSPOT II(T)/TRACK(C) data acquisition system and two Ki stler force plates at a sampling frequency of 153 Hz. Twenty-six discr ete data points were chosen from each trial for analysis. Each identif ied point detailed the intersection, separation, maximum or minimum va lue of CM, CP, or GRF in all three planes. Specific phases of SA and S D are presented and described. The actions of CM, CP, and GRF are pres ented during each phase. Results further refine the phases originally described by McFayden and Winter. Subtle differences in phases and dur ation of single and double support are demonstrated between SA and SD. Based on these results, it is apparent that SD is a more dynamic proc ess with greater inherent instability. Knowledge of SA and SD phases a nd CM/CP dynamics in healthy, normal subjects will permit comparison w ith patients exhibiting various pathologies. Such comparison should fa cilitate the development of appropriate intervention strategies.