) motion capture is limited as a clinical tool because of the time and expertise required for data collection or processing. The development of surrogate measures to assess knee kinetic symmetry may help to improve rehabilitation. Analysis of ground reaction force (GRF) symmetry using force plate
Aaron Nelson, Nathan Koslakiewicz and Thomas Gus Almonroeder
Jason Lake, Peter Mundy, Paul Comfort, John J. McMahon, Timothy J. Suchomel and Patrick Carden
Force plates are often used to measure countermovement vertical jump (CMJ) ability. This provides practitioners with information about the athletes’ capacity to accelerate their body mass using variables such as impulse, mean force, phase duration, 1 – 4 and the reactive strength index modified (i
Ryan Morrison, Kyle M. Petit, Chris Kuenze, Ryan N. Moran and Tracey Covassin
diagnostic accuracy and reliability. Due to the subjective nature of these tests, a force plate is considered the gold standard because of its objective outcome. 6 Force-plate analysis allows for the athlete center of pressure (COP) to be calculated based on the foot contact of an individual while on the
Gemma N. Parry, Lee C. Herrington and Ian G. Horsley
research analyzing upper-limb power production via a plyometric push-up, with only a few studies investigating force plate–derived kinetic data to assess upper-limb power output. 5 – 7 There is evidence of moderate to high reliability with strong test–retest correlations (intraclass correlation
Maury L. Hull, Richard Brewer and David Hawkins
This paper reports on the design, fabrication, and performance evaluation of a new force plate. The force plate is unique in that it can be manufactured “in house” using conventional machine tools for substantially lower cost than commercially available units. To achieve these attributes, the force plate embodies four octagonal strain ring sensing elements that are instrumented with conventional strain gauges. Strain gauge signals are amplified by simple signal conditioning circuits with a low component count. Despite the simplicity of the design, a calibration and accuracy check revealed root mean squared errors of 14 N for the vertical force component and less than 11 N for the horizontal force components.
John H. Challis
This study examined the influence of force plate targeting, via stride length adjustments, on the magnitude and consistency of ground reaction force and segment angle profiles of the stance phase of human running. Seven male subjects (height, 1.77 m ± 0.081; mass, 72.4 kg ± 7.52; age range, 23 to 32 years) were asked to run at a mean velocity of 3.2 m · s–1 under three conditions (normal, short, and long strides). Four trials were completed for each condition. For each trial, the ground reaction forces were measured and the orientations of the foot, shank, and thigh computed. There were no statistically significant differences (p > .05) between the coefficients of variation of ground reaction force and segment angle profiles under the three conditions, so these profiles were produced consistently. Peak active vertical ground reaction forces, their timings, and segment angles at foot off were not significantly different across conditions. In contrast, significant differences between conditions were found for peak vertical impact forces and their timings, and for the three lower limb segment angles at the start of force plate contact. These results have implications for human gait studies, which require subjects to target the force plate. Targeting may be acceptable depending on the variables to be analyzed.
Eamon T. Campolettano, Gunnar Brolinson and Steven Rowson
practice effect is variable. 26 Alternatively, a static balance assessment on a force plate consisting of eyes open and eyes closed trials has been used to assess athlete postural control. 20 , 27 – 36 These protocols typically track center of pressure trajectories to characterize balance. This
Christopher A. Bailey and Patrick A. Costigan
The step-up-and-over test has been used successfully to examine knee function after knee injury. Knee function is quantified using the following variables extracted from force plate data: the maximal force exerted during the lift, the maximal impact force at landing, and the total time to complete the step. For various reasons, including space and cost, it is unlikely that all clinicians will have access to a force plate. The purpose of the study was to determine if the step-up-and-over test could be simplified by using an accelerometer. The step-up-and-over test was performed by 17 healthy young adults while being measured with both a force plate and a 3-axis accelerometer mounted at the low back. Results showed that the accelerometer and force plate measures were strongly correlated for all 3 variables (r = .90–.98, Ps < .001) and that the accelerometer values for the lift and impact indices were 6–7% higher (Ps < .01) and occurred 0.07–0.1 s later than the force plate (Ps < .05). The accelerometer returned values highly correlated to those from a force plate. Compared with a force plate, a wireless, 3-axis accelerometer is a less expensive and more portable system with which to measure the step-up-and-over test.
John Goetschius, Mark A. Feger, Jay Hertel and Joseph M. Hart
control that occur following injury and rehabilitation. 1 – 3 For clinical purposes, it is essential that balance platforms demonstrate reliability and validity to detect changes in postural control due to losses of visual input, vestibular input, and/or somatosensory input. Laboratory grade force-plates
Tyler B. Weaver, Christine Ma and Andrew C. Laing
The Nintendo Wii Balance Board (WBB) has become popular as a low-cost alternative to research-grade force plates. The purposes of this study were to characterize a series of technical specifications for the WBB, to compare balance control metrics derived from time-varying center of pressure (COP) signals collected simultaneously from a WBB and a research-grade force plate, and to investigate the effects of battery life. Drift, linearity, hysteresis, mass accuracy, uniformity of response, and COP accuracy were assessed from a WBB. In addition, 6 participants completed an eyes-closed quiet standing task on the WBB (at 3 battery life levels) mounted on a force plate while sway was simultaneously measured by both systems. Characterization results were all associated with less than 1% error. R 2 values reflecting WBB sensor linearity were > .99. Known and measured COP differences were lowest at the center of the WBB and greatest at the corners. Between-device differences in quiet stance COP summary metrics were of limited clinical significance. Lastly, battery life did not affect WBB COP accuracy, but did influence 2 of 8 quiet stance WBB parameters. This study provides general support for the WBB as a low-cost alternative to research-grade force plates for quantifying COP movement during standing.