Studies investigating the effect of targeting on gait have focused on the analysis of ground reaction force (GRF) within the time domain. Analysis within the frequency domain may be a more sensitive method for evaluating variations in GRF. The aim of the present study was to investigate the effect of visual targeting on GRF analyzed within the frequency domain. A within-subject repeated-measures design was used to measure the mediolateral, vertical, and antero-posterior components of the GRF of 11 healthy volunteers while walking at their own pace over a paper-covered walkway. A 30 × 24-cm target area was superimposed over a hidden Kistler force plate mounted at the midpoint of the walkway. GRF were recorded with and without the target and were analyzed within the frequency domain. Although visually guided foot placement has previously been undetected by traditional time-domain measures, targeting was found to significantly increase the frequency content of both the mediolateral (t10 = -4.07, p < 0.05) and antero-posterior (t10 = -2.52, p < 0.05) components of GRF. Consequently, it appears that frequency analysis is a more sensitive analytic technique for evaluating GRF. These findings have methodological implications for research in which GRF is used to characterize and assess anomalies in gait patterns.
Scott C. Wearing, James E. Smeathers and Stephen R. Urry
Laurent Frossard, James Smeathers, Alison O’Riordan and Scott Goodman
The parameters of the shot’s trajectory were reported for male and female gold medalists (classes F52, F53, F54, and F55) who competed at the 2000 Paralympic Games and the 2002 International Paralympic Committee (IPC) World Championships. The specific objective was to determine the magnitude of differences in these parameters across classes and genders. The release velocity of the shot increased with the performance and the classification for both males (8.30 m/s – 9.96 m/s) and females (4.58 m/s – 8.50 m/s). The measured angle of the shot’s trajectory at release also increased with the performance and the classification for both males (27.54° – 32.47°) and females (9.02° – 34.52°). The position of the shot from a fixed reference point at release revealed a similar trend for both males (2.01 m – 2.68 m) and females (1.16 m – 1.98 m), although it was weaker.
Brendan Burkett, James Smeathers and Timothy M. Barker
For amputees to perform an everyday task, or to participate in physical exercise, it is crucial that they have an appropriately designed and functional prosthesis. Past studies of transfemoral amputee gait have identified several limitations in the performance of amputees and in their prosthesis when compared with able-bodied walking, such as asymmetrical gait, slower walking speed, and higher energy demands. In particular the different inertial characteristics of the prosthesis relative to the sound limb results in a longer swing time for the prosthesis. The aim of this study was to determine whether this longer swing time could be addressed by modifying the alignment of the prosthesis. The following hypothesis was tested: Can the inertial characteristics of the prosthesis be improved by lowering the prosthetic knee joint, thereby producing a faster swing time? To test this hypothesis, a simple 2-D mathematical model was developed to simulate the swing-phase motion of the prosthetic leg. The model applies forward dynamics to the measured hip moment of the amputee in conjunction with the inertial characteristics of prosthetic components to predict the swing-phase motion. To evaluate the model and measure any change in prosthetic function, we conducted a kinematic analysis on four Paralympic runners as they ran. When evaluated, there was no significant difference (p > 0.05) between predicted and measured swing time. Of particular interest was how swing time was affected by changes in the position of the prosthetic knee axis. The model suggested that lowering the axis of the prosthetic knee could reduce the longer swing time. This hypothesis was confirmed when tested on the amputee runners.