Changes In Ground Reaction Forces Research Articles

Effects of Acceleration on Ground Reaction Forces Collected in Healthy Dogs at a Trot

SummaryThe aim of this study was to assess, whether or not, visual grading of changes in subject acceleration during force plate collection within a fixed, measured velocity range was adequate to control acceleration/deceleration. A second question was, whether or not, visual grading of the trials was adequate to prevent significant changes in ground reaction forces within a controlled velocity range. Eight healthy, non-chondrodysplastic dogs, of varying breeds, were used in the study. Each dog was tested in four different protocols. The order in which the dogs completed the different protocols was determined randomly. During all of the protocols, the dogs trotted across the measured testing area within a velocity range of 1.6 to 1.9 m/s. The protocols varied in the amount of acceleration or deceleration allowed in the testing area and the methods of evaluating the acceleration or deceleration. Significant differences in ground reaction force measurements were found, with variations in the acceleration and deceleration. The majority of changes were found in the craniocaudal axis during acceleration and deceleration. Vertical axis measurements were only altered in the rear limbs. Significant differences were not found in any measurement (except the stance phase duration in the rear limb) between the mechanically controlled minimal acceleration/deceleration variation protocol and the visually controlled acceleration/deceleration variation protocol. While visual observation was unable to consistently differentiate acceleration, or deceleration, changes through the testing area, it was able to eliminate enough variation in ground reaction force measurements so that differences were not found between the mechanically controlled minimal acceleration/ deceleration variation protocol nor the visually controlled acceleration/deceleration variation protocol. These results suggest that either method of collection may be acceptable for data collection depending upon the type of study being performed.The effects of acceleration variation were examined in dogs undergoing force plate gait analysis. Significant differences in ground reaction force measurements were found, with variations in the acceleration and deceleration. The majority of changes were found in the craniocaudal axis, during acceleration and deceleration. Visual observation was unable to consistently differentiate variations in acceleration through the testing area.

The relation between limb loading and control parameters of gait initiation in persons with stroke

Objective: This study investigated the relation between limb loading and selected characteristics of gait initiation in patients after stroke. Subjects and Setting: Thirteen patients attending a rehabilitation clinic volunteered for the study. Design: For the description of clinical features, patients were divided into two groups dependent on the amount of body weight shared by the involved limb during stance before gait initiation. Main Outcome Measures: Patients performed six trials of gait initiation with either their involved or noninvolved limb on a force platform. Peak ground reaction forces and bilateral tibialis anterior and gastrocnemius electromyographic (EMG) activity were used for group comparison. Results: All patients showed the correct loading and unloading characteristics in the vertical and medial-lateral direction during gait initiation. Strong correlations were noted between initial limb loading and ground reaction forces during gait initiation ( r = .79 to .95). Changes in ground reaction forces were significantly less ( p < .001) for those patients who demonstrated decreased weight bearing on their involved limb before gait initiation. These patients were also unable to generate forward momentum, as evidenced by the fore-aft ground reaction force, with the involved limb. For all patients, increased gastrocnemius activity was noted in the stance (noninvolved) limb. The data are further discussed in regard to the relationship of the interaction of bilateral EMG activity and ground reaction forces. Conclusion: This study suggests that there is a correlation between symmetrical weight bearing and the ability to provide those forces than generate forward momentum in the initiation of gait.

Changes in ground reaction forces during rehabilitation of the above-knee amputee

Changes in ground reaction forces during rehabilitation of the above-knee amputee

Heel pad mechanics in shod conditions : Conflicting mechanics

GROUND REACTION FORCES IN SPRINTING Michiyoshi Ae*, Ken Miyashita*, Shoitiro Ooki*, and Takashi Yokoi** * Institute of Health and Sport Sciences, University of Tsukuba **Industrial Products Research Institute Tsukuba City, Ibaraki 305, JAPAN The purpose of this study was to investigate the changes in ground reaction forces (GRF) during sub-maximum and maximum sprinting. Fourteen male sprinters and jumpers were asked to make contact with a Kistler force platform with the maximum and the sub-maximum (ca. 80%) speeds. The analog signals of three orthogonal components of GRF were recorded and converted to data equivalent to sampling rate of 400 Hz. Impact type vs non-impact type:8 distinct difference was found in the vertical component. Nine subjects were categorized as an impact type and five subjects as a nonimpact type. Continuous lateral force in the 2nd half was seen in the non-impact type while the impact type showed fluctuating medio-lateral force. Regardless of the types, double peaked anterior force and single peaked posterior force were observec. Effects of sprinting speed:The most remarkable effect of speed was found in the vertical component of the impact type, i.e. double peaked pattern for the sub-maximum speed and for the maximum speed single peaked pattern with no relative minimum and no distinguished thrust peak. Impulse and average force of the 2nd half and the magnitude of force at the midpoint were larger in the sub-maximum than the maximum speed. These results and geometry of the support leg for the impact type suggestea that the force exerted by the leg muscles, especially the plantarflexors was smaller for the 2nd half in the maximum speed than the sub-maximum speed.

Dynamic transitions in stance support accompanying leg flexion movements in man

The control processes underlying dynamic transitions in stance support during single leg flexion movements were investigated in human subjects as a function of the intended speed of movement, by examining the vertical and lateral horizontal components of the ground reaction forces, the frontal plane trajectory of the body center of mass (CM) recorded via motion analysis, and the electromyographic (EMG) recordings of selected lower limb muscles. For the slowest movements, the measured vertical force beneath the flexing and single stance limbs closely matched the vertical force-time history predicted by a quasi-static mechanical model, whereas, the more rapid natural and fast speeds showed progressively larger discrepancies between measured and predicted forces. The initial resultant horizontal force component was exerted in the flexing to stance limb direction but was proportionately greater (4:1) beneath the flexing versus the stance limb during fast and natural speeds, and became equivalent for slow movements. Speed related EMG differences included an early phasic recruitment of the lateral hip muscle of the flexing limb which always preceded the ground reaction force changes for fast and natural but not slow movements, and a considerably earlier onset of the stance leg knee extensor relative to the flexing limb knee flexor for slow versus fast and natural speeds. Overall, the findings suggested two different speed related strategies for linking the postural and intentional movement components, where the choice of the strategy selected appeared to reflect the mechanical requirements needed to overcome the inertial force of the body mass during transitions from bipedal to single limb stance support.

Analysis of standing up and sitting down in humans: Definitions and normative data presentation

A formal definition of human standing up and sitting down movements based on sagittal plane goniometric and force plate data from 20 normal subjects is presented. This definition is comparable to the established gait cycle diagram, and consists of defined characteristic events and relative time intervals between them. The characteristic events are selected primarily on changes in ground reaction forces. The terminology proposed may be valuable for introducing more formalized and standardized reporting of both qualitative and quantitative studies in both normals and in patients. This presentation is directed toward the process of defining generally acceptable standards for human standing up and sitting down movements.

Timing of the Lower Limb Drive and Throwing Limb Movement in Baseball Pitching

Eight international baseball pitchers were filmed in a laboratory while throwing from a pitching rubber attached to a Kistler force platform. Following a warm-up, all subjects threw fastballs (FB) until two strike pitches were assessed by an umpire positioned behind the catcher for both wind-up and set pitching techniques. Subjects then followed the same procedures for curveball pitches (CB). Both vertical (Z) and horizontal (Y) ground reaction force (GRF) data were recorded. A shutter correlation pulse was encoded so the temporal data from the film could be synchronized with the kinetic data from the force platform. Analysis of variance was used to analyze differences in force data at selected points in both pitching actions for both techniques. Vertical and horizontal GRFs increased from the first balance position to maximum levels at the cocked position for both techniques. Nonsignificant changes in GRF then occurred between the cocked position and front-foot landing. The Z GRFs were similar throughout the pitching action but higher in magnitude for the CB compared to the FB. Mean resultant forces were similar for the three fastest FB pitchers when compared to the three slowest pitchers. However, the slower group produced their peak resultant force earlier in the action, thus reducing the ability to drive over a stabilized front leg.

Interaction between man and shoe in running: considerations for a more comprehensive measurement approach.

Man-shoe-surface interaction in running is a complex phenomenon, and its investigation gives specific requirements for the measuring system. This study was designed to make an effort to develop a methodology for measuring the interaction between the first two components (man and shoe) under normal heel running conditions both on the force plate and on an asphalt road. The force plate system consisted of a series of 1.5-m long plates with a total length of 12 m. This allowed recordings of several natural ground contact phases in one run. By repeating the runs several times at constant velocity (3 m X s-1 and 5 m X s-1), altogether 10-30 Fz and Fx force curves could be obtained for further computerized averaging. The running shoes were equipped with special heel and toe contact sensors, which were used for recordings of even more cycles at constant velocity on the road running conditions. Telemetered EMG technique was employed to examine the response of the selected lower extremity muscles on the varying shoe and running velocity conditions. The results indicated preliminarily that the changes in ground reaction forces were more velocity than shoe (hard/soft) dependent and that EMG activation patterns were muscle specific with regard to preinnervation and impact and push-off phases for the gastrocnemius, rectus femoris, vastus lateralis, and tibialis anterior muscles. Although the actual measurements were not yet designed for comprehensive recording of each parameter, the results obtained suggest that the major leg extensor muscles change their activation patterns with the varying impact load conditions.(ABSTRACT TRUNCATED AT 250 WORDS)