Peak Propulsive Force Research Articles

Reliability of a Unilateral Horizontal Leg Power Test to Assess Stretch Load Tolerance

Drop jumping has previously been used to measure fast stretch shorten cycle (SSC) ability and stretch load tolerance. To the knowledge of these authors a test does not exist to achieve this in the horizontal direction. The purpose of this study therefore was to estimate the reliability of a new unilateral horizontal leg power test to assess these qualities. Participants (N = 10) performed three jumps on each leg from distances of 80%, 120%, and 160% of leg length onto a force plate, followed immediately by a jump for maximal distance onto a synthetic track. No significant between- leg differences (p > .05) were found for the dependent variables of ground contact time (GCT), peak propulsive vertical ground reaction force, peak propulsive horizontal ground reaction force, and distances jumped (DJ).Within-trial variability (coefficients of variation) ranged from 3.6% to 10.9%, and test-retest reliability intraclass correlation coefficients from 0.80 to 0.95. GCT and DJ were the variables with highest reliability between trials and days. These two variables should be used to indicate fast SSC (GCT) ability and stretch load tolerance (DJ-GCT) in the horizontal direction. The relationship of these measures to functional performance needs to be established.

Force Plate Analysis Before and After Dorsal Decompression for Treatment of Degenerative Lumbosacral Stenosis in Dogs

Using force plate analysis (FPA), determine ground reaction forces in dogs with degenerative lumbosacral stenosis (DLS) and evaluate the effects of lumbosacral decompressive surgery. Prospective clinical study. Twelve dogs with DLS. DLS was diagnosed by clinical signs, radiography, computed tomography, and/or magnetic resonance imaging. FPA was performed before surgery, and 3 days, 6 weeks, and 6 months after surgery. The mean peak braking (Fy+), peak propulsive (Fy-), and peak vertical (Fz+) forces of 8 consecutive strides were determined. The ratio between the total Fy- of the pelvic limbs and the total Fy- of the thoracic limbs (P/TFy-), reflecting the distribution of Fy-, was analyzed to evaluate any changes in locomotion pattern postoperatively. Ground reaction force data for DLS dogs were compared with data derived from 24 healthy dogs (control). In dogs with DLS, the propulsive forces (Fy-) of the pelvic limbs were significantly smaller than those of controls. P/TFy- was significantly smaller in dogs with DLS than in control dogs, and increased during the follow-up period, reaching normal values 6 months after surgery. Cauda equina compression in dogs with DLS decreases the propulsive force of the pelvic limbs and surgical treatment restores the propulsive force of the pelvic limbs in a 6-month period. In dogs with DLS, FPA is an effective method in evaluating the response to surgical treatment. Normal propulsive force in the pelvic limbs was restored during 6 months after decompressive surgery.

Temporal stride and force analysis of cane-assisted gait in people with hemiplegic stroke

Chen C-L, Chen H-C, Wong M-K, Tang F-T, Chen R-S. Temporal stride and force analysis of cane-assisted gait in people with hemiplegic stroke. Arch Phys Med Rehabil 2000;81:43-8. Objective: To understand the underlying biomechanics of temporal stride and force in people with hemiplegic stroke during cane-assisted walking. Design: Three forceplates, 6 cameras, and an instrumented cane were integrated to analyze the cane-assisted gait of people with hemiplegic stroke. Temporal-stride parameters, and peak vertical, anterior (propulsive), posterior (braking), and lateral shear forces, as well as propulsive-breaking impulses were analyzed. Setting: Chang Gung Memorial Hospital, Medical Center, Taiwan. Participants: Twenty people with hemiplegic stroke. Main Outcome Measures: Temporal-stride and force parameters. Results: All patients walked at a relatively slow speed, ranging from 4.2 to 35.8cm/s. The triple and double support occupied most of the gait cycle (GC), whereas the single support occupied only 10% of GC. The applied vertical, propulsive, braking, and lateral shear forces on either foot and the cane were 89.7% to 97.6%, 2.2% to 4.8%, 2.9% to 3.9%, and 5.5% to 6.7% body weight (BW), respectively. Patients applied less than 25% BW of peak vertical forces on the cane. They applied greater peak propulsive forces and impulses on the sound foot, while applying greater peak braking forces and impulses on the affected foot and cane. Conclusions: The cane provided support and a braking function for people with hemiplegic stroke. People with stroke walking with cane assistance rely mostly on the sound limb for propulsion, while using the affected limb and cane for braking. Data provided could be useful in assessing the nature of cane assistance and in planning therapeutic strategies for people with stroke. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Investigating Kinetics in the Freestyle Flip Turn Push-Off

Thirty experienced male swimmers with body types ± 1 SD of the mean of selected body form parameters reported for elite male swimmers were recruited for the study. During three freestyle flip turns, selected kinetic, hydrodynamic, and kinematic variables of the push-off following a flip turn were recorded. Kinetics were recorded via a 2D vertically mounted forceplate that recorded peak push-off force and total impulse. The acceleration of each swimmer’s center of gravity and wall exit velocity were calculated from underwater videography. Hydrodynamic peak drag force and drag impulse were calculated from the kinetic and kinematic data using a derivative of Newton’s second law. A stepwise regression yielded peak drag force, peak propulsive force, and push-off time in the final regression equation (R = 0.80; R2 = 0.64). Beta values indicated that the peak drag force carried the highest weighting of the three variables. The results of the stepwise regression indicated that a combination of a low peak drag force high peak propulsive force, and increased wall push-off time produced the fastest final push-off velocity.

The Effect of Quadriceps Femoris, Hamstring, and Placebo Eccentric Fatigue on Knee and Ankle Dynamics During Crossover Cutting

This study attempted to determine the effect of eccentric quadriceps femoris, hamstring, and placebo fatigue on stance limb dynamics during the plant-and-cut phase of a crossover cut. Twenty female college students (task trained) were tested. Hamstring fatigue resulted in decreased peak impact knee flexion moments (p < or = .01), increased internal tibial rotation at peak knee flexion (p < or = .05), and decreased peak ankle dorisflexion (p < or = .05). Quadriceps fatigue resulted in increased peak ankle dorsiflexion moments (p < .01), decreased peak posterior braking forces (p < or .01), decreased peak knee extension moments (p < or = .01), delayed peak knee flexion (p < or = .01), delayed peak propulsive forces (p < .01), and delayed subtalar peak inversion moments (p < or = .05). Fatigue of either muscle group produced earlier peak ankle plantar flexion moments (p < = .05) and decreased peak propulsive knee flexion moments (p < or = .05). Variables requiring further study (p < or = .1) provide discussion data. Soleus, gastrocnemius, tibialis anterior, and deep posterior compartment calf muscles serve as dynamic impact force attenuators, compensating for fatigued proximal muscles.

Long-term Results of Conservative Treatment, Excision Arthroplasty and Triple Pelvic Osteotomy for the Treatment of Hip Dysplasia in the Immature Dog

SummaryThe long-term efficiency of conservative treatment, excision arthroplasty of the femoral head and neck and triple pelvic osteotomy for the treatment of hip dysplasia in the immature dog were compared using ground reaction forces analysis at the trot. Fourteen hips were re-evaluated for the conservative treatment group, 16 for the triple pelvic osteotomy group and ten for the excision arthroplasty group. Force plate analysis demonstrated that hind limbs belonging to the triple pelvic osteotomy group had, at the trot, a locomotor function similar to the one of normal hind limbs in the control group. At a “similar age”, hind limbs of the conservative group did not show any marked difference from those in the triple pelvic osteotomy and control groups. The dogs of the excision arthroplasty group showed ground reaction forces abnormalities, most probably due to the absence of a coxofemoral joint (decreased peak propulsive force and Fz impulse, compared to triple pelvic osteotomy and control groups). The forelimbs of conservative treatment, excision arthroplasty and triple pelvic osteotomy groups showed a peak propulsive force superior to the one in the control group. This could be an adaptation phenomenon in order to compensate a deficient function of the hind limbs or a habit acquired at a younger age.Force plate analysis has demonstrated that hind limbs treated bilaterally with triple pelvic osteotomy had, at the trot, a locomotor function similar to the one of normal hind limbs from a control group. At a mean age of 4.5 ± 1 years, dogs treated conservatively did not show, at the trot, any marked difference with those treated with triple pelvic osteotomy and with normal dogs. Hind limbs treated with excision arthroplasty showed certain abnormalities most probably due to the absence of a coxofemoral joint such as a significant decrease of peak propulsive force and Fz impulse.