Analysis of the impulse of the ground reaction force in normal gait
Okumura, S.
Nihon Seikeigeka Gakkai Zasshi 57(3): 309-320
1983
ISSN/ISBN: 0021-5325 PMID: 6864042 Document Number: 214579
The ground reaction force (GRF) is produced as a vector. A force plate divides it into 3 components (vertical, fore-aft and lateral). Traditional analysis of the GRF was directed to these 3 components. It is difficult to study the GRF by this method. The impulse of the GRF and its direction in the sagittal plane were analyzed. Subjects were 14 men and 16 women aged 18-39 yr. They walked 10 times on Kistler's force plate at 80, 100, 120 and 140 steps/ min using a metronome as a pacesetter. The impulse of the resultant, vertical and fore-aft forces was analyzed by microcomputer. The direction of the resultant force in the sagittal plane was obtained at the peaks of the fore-aft force in the restrictive period and the propulsive period, respectively, as follows; .theta. = arctan FYP/FZP . The impulse per body weight of the resultant force during a stance phase (.SIGMA.FR/W) decreased with increases in cadence. This was the case for both .SIGMA.FR1/W of the restrictive period and .SIGMA.FR2/W of the propulsive period. The former was always greater than the latter. .SIGMA.FR/W .cntdot. t changed little with increases in cadence (.SIGMA.FR/W per 10 ms). However, comparing .SIGMA.FR1/W .cntdot. t of the restrictive period and .SIGMA.FR2/W .cntdot. t of the propulsive period, .SIGMA.FR1/W .cntdot. t increased but .SIGMA.FR2/W .cntdot. t decreased linearly with increases in cadence. The value of the vertical force was nearly the same as the resultant force and this was also observed as the cadence increased. The impulse per body weight of the fore-aft force during a stance phase (.SIGMA. FY /W) also decreased with increases in cadence. Both .SIGMA. FY1 /W of the restrictive period and .SIGMA. FY2 /W of the propulsive period decreased with increases in cadence. Comparing .SIGMA. FY1 /W and .SIGMA. FY2 /W, the latter was always greater than the former. .SIGMA. FY /W .cntdot. t increased with increases in cadence (.SIGMA. FY /W per 10 ms). Both .SIGMA. FY1 /W .cntdot. t and .SIGMA. FY2 /W .cntdot. t increased with increases in cadence. However, .SIGMA.FR/W .cntdot. t remained fairly constant with increases in cadence. The angle (.theta.1) of the resultant force in the restrictive period was always smaller than the angle (.theta.2) in the propulsive period. .theta.1 increased slightly but .theta.2 increased greatly with increases in cadence.