RESUMO
It has been proposed that the highly reproducible forward walking (FW) locomotor pattern is generated by a central neuronal program or central pattern generator (CPG) which provides the underlying mechanism which produces the coordinated walking movement. The purpose of this study was to quantify the differences in the muscular activation patterns during FW and backward walking (BW) at a constant step frequency and to determine if common features exist across both locomotor conditions. The hypothesis was that FW and BW are both mediated by the same CPG; therefore, only small modifications in the CPG are required in order to produce the different characteristics of each walking mode. The results noted kinematically reversed patterns at the hip and ankle joints between FW and BW. The knee joint movement pattern was similar between conditions, however, a phase shift of 14.3% of the gait cycle occurred. An approximately 25% phase shift in the muscle activation patterns existed between FW and BW in four of the six muscles studied. Additionally, a pattern recognition technique was applied to the combined EMG signals to determine the minimum number of features required to generate the measured muscular output. Only two main features were necessary to produce the EMG patterns for both the FW and BW condition. The main features in FW were more consistent than noted in BW. The results support the notion that a single spinal mechanism such as a CPG with two main features appears to be in control during both FW and BW. Copyright 1998 Elsevier Science B.V. All rights reserved
RESUMO
INTRODUCTION:: With increasing frequency, harness-supported treadmill ambulation has been advocated in patient use in order to provide reduction in weight-bearing to healing tissues and as a method which reduces the energy cost of treadmill ambulation. The purpose of this study was to analyse the ability of one of these devices (Zuni Exercise System) to support a percentage of a subject's body weight during walking and running and to explore the relationship of unloading to pressure reduction in selected plantar surface regions of the foot. METHODS:: Ten healthy male volunteers with no known foot pathology participated in this study. In-shoe plantar pressure (PEDAR) and vertical ground reaction force (GRF) were measured during walking and running at full body weight and at a 20% body[Figure: see text][Figure: see text] weight supported setting. Statistical evaluation used a one way ANOVA and a post-hoc paired t-test with significance set at p < 0.05. RESULTS:: Walking with a setting of 20% body weight supported was achieved with a reduction of the first and second vertical force peaks of 23.8+/-7.3% and 27.2+/-4.1% respectively, somewhat greater than the selected setting (Figure 1). The total force time integral during walking unloaded was 22.8+/-3.3%, which was only slightly greater than the selected 20% reduction. During running the active vertical force peak and total force time integral were reduced by 19.9+/-6.0% and 20.0+/-3.3% respectively during the unloaded condition (Figure 2). Plantar pressures were reduced from 6.8 - 27.8% during body weight supported conditions. The reduction in plantar pressure was variable across different regions of the foot with the toes in walking and the medial forefoot region in running being the least unloaded. DISCUSSION AND CONCLUSIONS:: The Zuni Exercise System appears to be a valid device to predictably reduce the vertical component of the GRF during walking and running with 20% body weight supported. Plantar pressures were reduced during body weight supported conditions but the reduction varied at different regions of the foot. However, the variability of the reduction across subjects was substantial, implying that a given regional pressure may not be as predictably reduced during a body weight supported condition. This highlights the difficulty a practitioner has in the ability to confidently reduce pressure by a set amount in a selected foot region by using assistive devices without direct in-shoe measurements.
