scholarly journals Estimates of Running Ground Reaction Force Parameters from Motion Analysis

2017 ◽  
Vol 33 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Gaspare Pavei ◽  
Elena Seminati ◽  
Jorge L.L. Storniolo ◽  
Leonardo A. Peyré-Tartaruga
Keyword(s):  
Motion Analysis ◽  
Ground Reaction Force ◽  
Center Of Mass ◽  
Reaction Force ◽  
The Body ◽  
Vertical Force ◽  
Vertical Stiffness ◽  
Leg Stiffness ◽  
Force Peak ◽  
Body Center

We compared running mechanics parameters determined from ground reaction force (GRF) measurements with estimated forces obtained from double differentiation of kinematic (K) data from motion analysis in a broad spectrum of running speeds (1.94–5.56 m⋅s–1). Data were collected through a force-instrumented treadmill and compared at different sampling frequencies (900 and 300 Hz for GRF, 300 and 100 Hz for K). Vertical force peak, shape, and impulse were similar between K methods and GRF. Contact time, flight time, and vertical stiffness (kvert) obtained from K showed the same trend as GRF with differences < 5%, whereas leg stiffness (kleg) was not correctly computed by kinematics. The results revealed that the main vertical GRF parameters can be computed by the double differentiation of the body center of mass properly calculated by motion analysis. The present model provides an alternative accessible method for determining temporal and kinetic parameters of running without an instrumented treadmill.

Use of Ground Reaction Force Parameters in Predicting Peak Tibial Accelerations in Running

1993 ◽  
Vol 9 (4) ◽  
pp. 306-314 ◽  
Author(s):  
Ewald M. Hennig ◽  
Thomas L. Milani ◽  
Mario A. Lafortune
Keyword(s):  
Ground Reaction Force ◽  
Reaction Force ◽  
The Body ◽  
Force Platform ◽  
Good Prediction ◽  
Vertical Force ◽  
Force Peak ◽  
Power Frequency ◽  
Initial Force ◽  
Force Data

Ground reaction force data and tibial accelerations from a skin-mounted transducer were collected during rearfoot running at 3.3 m/s across a force platform. Five repetitive trials from 27 subjects in each of 19 different footwear conditions were evaluated. Ground reaction force as well as tibial acceleration parameters were found to be useful for the evaluation of the cushioning properties of different athletic footwear. The good prediction of tibial accelerations by the maximum vertical force rate toward the initial force peak (r2 = .95) suggests that the use of a force platform is sufficient for the estimation of shock-absorbing properties of sport shoes. If an even higher prediction accuracy is required a regression equation with two variables (maximum force rate, median power frequency) may be used (r2 = .97). To evaluate the influence of footwear on the shock traveling through the body, a good prediction of peak tibial accelerations can be achieved from force platform measurements.

Effect of Hopping Frequency on Bilateral Differences in Leg Stiffness

2013 ◽  
Vol 29 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Hiroaki Hobara ◽  
Koh Inoue ◽  
Kazuyuki Kanosue
Keyword(s):  
Ground Reaction Force ◽  
Center Of Mass ◽  
Reaction Force ◽  
Human Movement ◽  
Vertical Ground Reaction Force ◽  
Mass Model ◽  
Lower Extremity Injuries ◽  
Leg Stiffness ◽  
Significant Difference ◽  
Bilateral Differences

Understanding the degree of leg stiffness during human movement would provide important information that may be used for injury prevention. In the current study, we investigated bilateral differences in leg stiffness during one-legged hopping. Ten male participants performed one-legged hopping in place, matching metronome beats at 1.5, 2.2, and 3.0 Hz. Based on a spring-mass model, we calculated leg stiffness, which is defined as the ratio of maximal ground reaction force to maximum center of mass displacement at the middle of the stance phase, measured from vertical ground reaction force. In all hopping frequency settings, there was no significant difference in leg stiffness between legs. Although not statistically significant, asymmetry was the greatest at 1.5 Hz, followed by 2.2 and 3.0 Hz for all dependent variables. Furthermore, the number of subjects with an asymmetry greater than the 10% criterion was larger at 1.5 Hz than those at 2.2 and 3.0 Hz. These results will assist in the formulation of treatment-specific training regimes and rehabilitation programs for lower extremity injuries.

A Comparison of Computation Methods for Leg Stiffness During Hopping

2014 ◽  
Vol 30 (1) ◽  
pp. 154-159 ◽  
Author(s):  
Hiroaki Hobara ◽  
Koh Inoue ◽  
Yoshiyuki Kobayashi ◽  
Toru Ogata
Keyword(s):  
Ground Reaction Force ◽  
Stance Phase ◽  
Center Of Mass ◽  
Reaction Force ◽  
Sine Wave ◽  
Phase Method ◽  
Leg Stiffness ◽  
Mass Displacement ◽  
Male Subjects ◽  
Oscillation Method

Despite the presence of several different calculations of leg stiffness during hopping, little is known about how the methodologies produce differences in the leg stiffness. The purpose of this study was to directly compareKlegduring hopping as calculated from three previously published computation methods. Ten male subjects hopped in place on two legs, at four frequencies (2.2, 2.6, 3.0, and 3.4 Hz). In this article, leg stiffness was calculated from the natural frequency of oscillation (method A), the ratio of maximal ground reaction force (GRF) to peak center of mass displacement at the middle of the stance phase (method B), and an approximation based on sine-wave GRF modeling (method C). We found that leg stiffness in all methods increased with an increase in hopping frequency, butKlegvalues using methods A and B were significantly higher than when using method C at all hopping frequencies. Therefore, care should be taken when comparing leg stiffness obtained by method C with those calculated by other methods.

A treadmill-mounted force platform

1989 ◽  
Vol 67 (4) ◽  
pp. 1692-1698 ◽  
Author(s):  
R. Kram ◽  
A. J. Powell
Keyword(s):  
Full Range ◽  
Center Of Mass ◽  
Reaction Force ◽  
Vertical Displacement ◽  
The Body ◽  
Force Platform ◽  
Vertical Force ◽  
Vertical Ground Reaction Force ◽  
Contact Phase ◽  
Frictional Forces

Muscle, bone, and tendon forces; the movement of the center of mass, and the spring properties of the body during terrestrial locomotion can be measured using ground-mounted force platforms. These measurements have been extremely time consuming because of the difficulty in obtaining repeatable constant speed trials (particularly with animals). We have overcome this difficulty by mounting a force platform directly under the belt of a motorized treadmill. With this arrangement, vertical force can be recorded from an unlimited number of successive ground contacts in a much shorter time. With this treadmill-mounted force platform it is possible to accurately make the following measurements over the full range of steady speeds and under various perturbations of normal gait: 1) vertical ground reaction force over the course of the contact phase; 2) peak forces in bone, muscle, and tendon; 3) the vertical displacement of the center of mass; and 4) contact time for the limbs. In our treadmill-force platform design, belt forces and frictional forces cause no measurable cross-talk problem. Natural frequency (160 Hz), nonlinearity (less than 5%), and position independence (less than 2%) are all quite acceptable. Motor-caused vibrations are greater than 150 Hz and thus can be easily filtered.

Mechanics of running under simulated low gravity

1991 ◽  
Vol 71 (3) ◽  
pp. 863-870 ◽  
Author(s):  
J. P. He ◽  
R. Kram ◽  
T. A. McMahon
Keyword(s):  
Normal Gravity ◽  
Human Subjects ◽  
Center Of Mass ◽  
The Body ◽  
Vertical Force ◽  
Low Gravity ◽  
Vertical Stiffness ◽  
Mass Spring Model ◽  
Linear Spring ◽  
Mass Spring

Using a linear mass-spring model of the body and leg (T. A. McMahon and G. C. Cheng. J. Biomech. 23: 65–78, 1990), we present experimental observations of human running under simulated low gravity and an analysis of these experiments. The purpose of the study was to investigate how the spring properties of the leg are adjusted to different levels of gravity. We hypothesized that leg spring stiffness would not change under simulated low-gravity conditions. To simulate low gravity, a nearly constant vertical force was applied to human subjects via a bicycle seat. The force was obtained by stretching long steel springs via a hand-operated winch. Subjects ran on a motorized treadmill that had been modified to include a force platform under the tread. Four subjects ran at one speed (3.0 m/s) under conditions of normal gravity and six simulated fractions of normal gravity from 0.2 to 0.7 G. For comparison, subjects also ran under normal gravity at five speeds from 2.0 to 6.0 m/s. Two basic principles emerged from all comparisons: both the stiffness of the leg, considered as a linear spring, and the vertical excursion of the center of mass during the flight phase did not change with forward speed or gravity. With these results as inputs, the mathematical model is able to account correctly for many of the changes in dynamic parameters that do take place, including the increasing vertical stiffness with speed at normal gravity and the decreasing peak force observed under conditions simulating low gravity.

Relationships between Ground Reaction Force and Tibial Bone Acceleration Parameters

1991 ◽  
Vol 7 (3) ◽  
pp. 303-309 ◽  
Author(s):  
Ewald M. Hennig ◽  
Mario A. Lafortune
Keyword(s):  
Ground Reaction Force ◽  
Reaction Force ◽  
Time Shift ◽  
Vertical Force ◽  
Time To Peak ◽  
Axial Acceleration ◽  
Force Peak ◽  
Tibial Acceleration ◽  
Using Data ◽  
Force Data

Using data from six male subjects, this study compared ground reaction force and tibial acceleration parameters for running. A bone-mounted triaxial accelerometer and a force platform were employed for data collection. Low peak values were found for the axial acceleration, and a time shift toward the occurrence of the first peak in the vertical force data was present. The time to peak axial acceleration differed significantly from the time to the first force peak, and the peak values of force and acceleration demonstrated only a moderate correlation. However, a high negative correlation was found for the comparison of the peak axial acceleration with the time to peak vertical force. Employing a multiple regression analysis, the peak tibial acceleration could be well estimated using vertical force loading rate and peak horizontal ground reaction force as predictors.

scholarly journals Reliability of Unilateral Vertical Leg Stiffness Measures Assessed During Bilateral Hopping

2015 ◽  
Vol 31 (5) ◽  
pp. 285-291 ◽  
Author(s):  
Sean J. Maloney ◽  
Iain M. Fletcher ◽  
Joanna Richards
Keyword(s):  
Coefficient Of Variation ◽  
Center Of Mass ◽  
Reaction Force ◽  
Force Plate ◽  
Vertical Stiffness ◽  
Coefficients Of Variation ◽  
Leg Stiffness ◽  
Average Coefficient ◽  
Left And Right ◽  
Stiffness Profile

The assessment of vertical leg stiffness is an important consideration given its relationship to performance. Vertical stiffness is most commonly assessed during a bilateral hopping task. The current study sought to determine the intersession reliability, quantified by the coefficient of variation, of vertical stiffness during bilateral hopping when assessed for the left and right limbs independently, which had not been previously investigated. On 4 separate occasions, 10 healthy males performed 30 unshod bilateral hops on a dual force plate system with data recorded independently for the left and right limbs. Vertical stiffness was calculated as the ratio of peak ground reaction force to the peak negative displacement of the center of mass during each hop and was averaged over the sixth through tenth hops. For vertical stiffness, average coefficients of variation of 15.3% and 14.3% were observed for the left and right limbs, respectively. An average coefficient of variation of 14.7% was observed for bilateral vertical stiffness. The current study reports that calculations of unilateral vertical stiffness demonstrate reliability comparable to bilateral calculations. Determining unilateral vertical stiffness values and relative discrepancies may allow a coach to build a more complete stiffness profile of an individual athlete and better inform the training process.

scholarly journals Mechanical demands of the two-handed hardstyle kettlebell swing performed by an RKC-certified Instructor

2021 ◽  
Author(s):  
Neil J. Meigh ◽  
Wayne A. Hing ◽  
Ben J. Schram ◽  
Justin W.L. Keogh
Keyword(s):  
Ground Reaction Force ◽  
Pearson Correlation ◽  
Reaction Force ◽  
Peak Force ◽  
Vertical Force ◽  
Strong Positive Correlation ◽  
Male Body ◽  
Positive Correlation ◽  
Force Peak ◽  
Force Time

Background: The effects of hardstyle kettlebell training are frequently discussed in the strength and conditioning field, yet reference data from a proficient swing is scarce. The aim of this study was to profile the mechanical demands of a two-handed hardstyle swing performed by a Russian Kettlebell Challenge (RKC) Instructor. Methods: The subject is a 44-year-old male, body mass 75.6 kg, height 173.5 cm, with 6 years of regular hardstyle kettlebell training since attaining certification in 2013. Two-handed hardstyle swings were performed with a series of incremental weight (8-68 kg) kettlebells. Ground reaction forces (GRFs) were obtained from a floor-mounted force platform. Force-time curves (FTCs), peak force, forward force relative to vertical force, rate of force development (RFD) and swing cadence were investigated. Results: Data revealed the FTC of a proficient swing were highly consistent (mean SD = 47 N) and dominated by a single force peak, with a profile that remained largely unchanged with 8-24 kg kettlebells. Pearson correlation analyses revealed a very strong positive correlation in peak force with kettlebell weight (r = 0.95), which increased disproportionately from the lightest to heaviest kettlebells; peak net force increasing from 8.36 ± 0.75 N.kg-1 (0.85 x BW) to 12.82 ± 0.39 N.kg-1 (1.3x BW). There was a strong negative correlation between RFD and kettlebell weight (r = 0.82) decreasing from 39.2 N.s-1.kg-1 to 21.5 N.s-1.kg-1. There was a very strong positive correlation in forward ground reaction force with kettlebell weight (r = 0.99), expressed as a ratio of vertical ground reaction, increasing from 0.092 (9.2%) to 0.205 (20.5%). Swing cadence exceeded 40 swings per minute (SPM) at all weights. Conclusion: Our findings challenge some of the popular beliefs of the hardstyle kettlebell swing. Consistent with hardstyle practice and previous kinematic analysis of expert and novice, force-time curves show a characteristic single large force peak, differentiating passive from active shoulder flexion. Ground reaction force did not increase proportionate to bell weight, with a magnitude of forward force smaller than described in practice. These results could be useful for coaches and trainers using kettlebells with the intent to improve athletic performance, and healthcare providers using the kettlebell swing for therapeutic purposes. Findings from this study were used to inform the BELL Trial, a pragmatic clinical trial of kettlebell training with older adults. www.anzctr.org.au ACTRN12619001177145.

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