Validation of a Torso-Mounted Accelerometer for Measures of Vertical Oscillation and Ground Contact Time During Treadmill Running

The purpose of this study was to validate measures of vertical oscillation (VO) and ground contact time (GCT) derived from a commercially-available, torso-mounted accelerometer compared with single marker kinematics and kinetic ground reaction force (GRF) data. Twenty-two semi-elite runners ran on an instrumented treadmill while GRF data (1000 Hz) and three-dimensional kinematics (200 Hz) were collected for 60 s across 5 different running speeds ranging from 2.7 to 3.9 m/s. Measurement agreement was assessed by Bland-Altman plots with 95% limits of agreement and by concordance correlation coefficient (CCC). The accelerometer had excellent CCC agreement (> 0.97) with marker kinematics, but only moderate agreement, and overestimated measures between 16.27 mm to 17.56 mm compared with GRF VO measures. The GCT measures from the accelerometer had very good CCC agreement with GRF data, with less than 6 ms of mean bias at higher speeds. These results indicate a torsomounted accelerometer provides valid and accurate measures of torso-segment VO, but both a marker placed on the torso and the accelerometer yield systematic overestimations of center of mass VO. Measures of GCT from the accelerometer are valid when compared with GRF data, particularly at faster running speeds.

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NFL Draft Prep Players Improve 40-Yard Run Times and Foot-Ground Kinetics

Research Directs in Strength and Performance ◽

10.53520/rdsp2021.1056 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Monique Mokha ◽

Tobin Silver ◽

Pete Bommarito

Keyword(s):

Contact Time ◽

National Football League ◽

Reaction Force ◽

American Football ◽

Football Players ◽

Ground Contact ◽

Vertical Ground Reaction Force ◽

Linear Speed ◽

Vertical Ground ◽

Ground Contact Time

Introduction: Linear speed is a discriminant factor between drafted and undrafted American football players into the National Football League. Linear speed is influenced by foot-ground contact time and the magnitude of vertical ground reaction force. The aim of this study was to determine if foot-ground kinetics during speed running could be modified through participating in a 6-week NFL draft preparation camp. Methods: To evaluate foot-ground kinetics, 16 American football players ran on an instrumented treadmill for 5 seconds at 6.5 m/s. Linear speed was measured during a 40-yard (36.6 m) outdoor run. Pre- and post-camp linear speed times, stance-averaged vertical ground reaction forces (vGRF, kg/N), foot-ground contact time (msec), and vertical impulse (kg/N * s) were examined using paired t-tests, p<.05. Results: Linear speed times significantly improved [(pre, 4.8±0.2 vs. post, 4.6±0.2 sec), t(15)=13.8, p<.001)], and foot-ground contact time significantly decreased for the right limb [(pre, 177+3.2 vs. post, 168+2.2 ms), t(15)=2.21, p=.043]. Mean vertical impulse and stance-averaged GRF for both limbs remained unchanged, p>.05. Conclusions: Linear speed and selected foot-ground kinetics are modifiable in NFL draft prep players. Training appears to lower 40-yard run times and foot-ground contact time.

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Effects of shoe weight on landing impact and side-to-side asymmetry

PLoS ONE ◽

10.1371/journal.pone.0256061 ◽

2021 ◽

Vol 16 (8) ◽

pp. e0256061

Author(s):

I-Lin Wang ◽

Jin-Jiang Gao ◽

Li-I Wang ◽

Ke-Ke Zhang

Keyword(s):

Ground Reaction Force ◽

Contact Time ◽

Reaction Force ◽

Ground Contact ◽

Drop Height ◽

Limb Injuries ◽

Ground Contact Time ◽

Force Time ◽

Leg Dominance ◽

Side Asymmetry

Shoes of different weights affect proprioception. Drop jump (DJ) tasks are often used to explore the risks and mechanisms of lower limb injuries. Leg dominance mainly refers to differences between the dominant and nondominant legs. Eight males and eight females participated in this study. The weights of the shoes in this investigation were 255 g, 335 g, and 415 g, and the heights of the DJ were 30 cm, 40 cm, and 50 cm. The side-to-side asymmetry of the time of contact initiation for the 30DJ was greater than that of the 40DJ and 50DJ, and the asymmetry for shoes weighing 415 g and 355 g was greater than that for shoes weighing 255 g. When the drop height increased, the side-to-side asymmetry of the peak ground reaction force (PGRF). also increased. The ground contact time increased as the drop height increased to 50DJ. Higher drop heights caused greater side-to-side asymmetry of the PGRF. Heavier shoes caused the peak ground reaction force time (PGRFT) in the nondominant leg to appear earlier, reduced the jump height and affected the performance. Heavier shoes caused greater side-to-side asymmetry at the initial ground contact and at the ground contact time, affecting training effectiveness.

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Validation of Garmin Fenix 3 HR Fitness Tracker Biomechanics and Metabolics (VO2max)

Journal for the Measurement of Physical Behaviour ◽

10.1123/jmpb.2019-0066 ◽

2020 ◽

Vol 3 (4) ◽

pp. 331-337 ◽

Cited By ~ 1

Author(s):

Bryson Carrier ◽

Andrew Creer ◽

Lauren R. Williams ◽

Timothy M. Holmes ◽

Brayden D. Jolley ◽

...

Keyword(s):

Contact Time ◽

Stride Length ◽

Percentage Error ◽

Vertical Oscillation ◽

Ground Contact ◽

Ground Contact Time ◽

Fitness Tracker ◽

System Variables ◽

Post Hoc ◽

Running Biomechanics

The purpose of this study was to determine the validity of the Garmin fēnix® 3 HR fitness tracker. Methods: A total of 34 healthy recreational runners participated in biomechanical or metabolic testing. Biomechanics participants completed three running conditions (flat, incline, and decline) at a self-selected running pace, on an instrumented treadmill while running biomechanics were tracked using a motion capture system. Variables extracted were compared with data collected by the Garmin fēnix 3 HR (worn on the wrist) that was paired with a chest heart rate monitor and a Garmin Foot Pod (worn on the shoe). Metabolic testing involved two separate tests; a graded exercise test to exhaustion utilizing a metabolic cart and treadmill, and a 15-min submaximal outdoor track session while wearing the Garmin. 2 × 3 analysis of variances with post hoc t tests, mean absolute percentage errors, Pearson’s correlation (R), and a t test were used to determine validity. Results: The fēnix kinematics had a mean absolute percentage errors of 9.44%, 0.21%, 26.38%, and 5.77% for stride length, run cadence, vertical oscillation, and ground contact time, respectively. The fēnix overestimated (p < .05) VO2max with a mean absolute percentage error of 8.05% and an R value of .917. Conclusion: The Garmin fēnix 3 HR appears to produce a valid measure of run cadence and ground contact time during running, while it overestimated vertical oscillation in every condition (p < .05) and should be used with caution when determining stride length. The fēnix appears to produce a valid VO2max estimate and may be used when more accurate methods are not available.

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Associations between Well-Being State and Match External and Internal Load in Amateur Referees

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18063322 ◽

2021 ◽

Vol 18 (6) ◽

pp. 3322

Author(s):

Eñaut Ozaeta ◽

Javier Yanci ◽

Carlo Castagna ◽

Estibaliz Romaratezabala ◽

Daniel Castillo

Keyword(s):

External Load ◽

Contact Time ◽

Well Being ◽

Ground Contact ◽

Internal Load ◽

Match Play ◽

Power Meter ◽

Ground Contact Time ◽

Training Impulse ◽

External Loads

The main aim of this paper was to examine the association between prematch well-being status with match internal and external load in field (FR) and assistant (AR) soccer referees. Twenty-three FR and 46 AR participated in this study. The well-being state was assessed using the Hooper Scale and the match external and internal loads were monitored with Stryd Power Meter and heart monitors. While no significant differences were found in Hooper indices between match officials, FR registered higher external loads (p < 0.01; ES: 0.75 to 5.78), spent more time in zone 4 and zone 5, and recorded a greater training impulse (TRIMP) value (p < 0.01; ES: 1.35 to 1.62) than AR. Generally, no associations were found between the well-being variables and external loads for FR and AR. Additionally, no associations were found between the Hooper indices and internal loads for FR and AR. However, several relationships with different magnitudes were found between internal and external match loads, for FR, between power and speed with time spent in zone 2 (p < 0.05; r = −0.43), ground contact time with zone 2 and zone 3 (p < 0.05; r = 0.50 to 0.60) and power, speed, cadence and ground contact time correlated with time spent in zone 5 and TRIMP (p < 0.05 to 0.01; r = 0.42 to 0.64). Additionally, for AR, a relationship between speed and time in zone 1 was found (p < 0.05; r = −0.30; CL = 0.22). These results suggest that initial well-being state is not related to match officials’ performances during match play. In addition, the Stryd Power Meter can be a useful device to calculate the external load on soccer match officials.

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The Effects of Muscle Energy on Low Back Pain: A 3D Analysis of running biomechanics

International Journal of Kinesiology and Sports Science ◽

10.7575/aiac.ijkss.v.9n.1p.51 ◽

2021 ◽

Vol 9 (1) ◽

pp. 51

Author(s):

Alisa Drapeaux ◽

Jon Hurdelbrink

Keyword(s):

Low Back Pain ◽

Back Pain ◽

Reaction Force ◽

Low Back ◽

Ground Contact ◽

Peak Acceleration ◽

Clinical Exam ◽

Ground Contact Time ◽

Muscle Energy ◽

Initial Peak

Background: Muscle energy technique (MET) is asn osteopathic treatment technique that is utilized frequently in the clinical setting, yet the overall effectiveness is minimally supported within literature. MET is an osteopathic technique that involves an isometric contract relax technique intended to improve alignment and enhance neuromuscular education. Objective: The purpose of this study was to determine the effectiveness of MET on running kinetics on subjects with low back pain. Method: A quasi-experimental research design was implemented and subjects, all of whom either had a history of or currently experience low back pain, underwent pre-intervention data collection of: anthropometric measurements, medical history, dorsaVi 3D running analysis, and a musculoskeletal and neurological clinical exam. Subjects underwent 6 weeks of isolated lumbo-pelvic MET at a frequency of twice a week, and were instructed to avoid all other treatment. Post-intervention data collected included a clinical exam and another dorsaVI running analysis. Results: Data was analyzed including: pre and post-treatment initial peak acceleration, ground contact time, and ground reaction force. A paired t-test comparing pre and post mean kinetic changes demonstrated the following p values: initial peak acceleration p = .80, ground contact time p = .96, and ground reaction force p = .68. Conclusion: This study demonstrated that isolated MET treatment is not statistically significant for changing 3D kinetic running variable in subjects with low back pain. Clinical Implications: Recommend healthcare providers to use a multi-treatment approach for low back pain. Future research should include a control group and larger sample size.

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Three-dimensional data-tracking simulations of sprinting using a direct collocation optimal control approach

PeerJ ◽

10.7717/peerj.10975 ◽

2021 ◽

Vol 9 ◽

pp. e10975

Author(s):

Nicos Haralabidis ◽

Gil Serrancolí ◽

Steffi Colyer ◽

Ian Bezodis ◽

Aki Salo ◽

...

Keyword(s):

Experimental Data ◽

Reaction Force ◽

Three Dimensional ◽

Contact Model ◽

Model Parameters ◽

Ground Contact ◽

Control Approach ◽

Average Percentage ◽

Data Tracking ◽

The Individual

Biomechanical simulation and modelling approaches have the possibility to make a meaningful impact within applied sports settings, such as sprinting. However, for this to be realised, such approaches must first undergo a thorough quantitative evaluation against experimental data. We developed a musculoskeletal modelling and simulation framework for sprinting, with the objective to evaluate its ability to reproduce experimental kinematics and kinetics data for different sprinting phases. This was achieved by performing a series of data-tracking calibration (individual and simultaneous) and validation simulations, that also featured the generation of dynamically consistent simulated outputs and the determination of foot-ground contact model parameters. The simulated values from the calibration simulations were found to be in close agreement with the corresponding experimental data, particularly for the kinematics (average root mean squared differences (RMSDs) less than 1.0° and 0.2 cm for the rotational and translational kinematics, respectively) and ground reaction force (highest average percentage RMSD of 8.1%). Minimal differences in tracking performance were observed when concurrently determining the foot-ground contact model parameters from each of the individual or simultaneous calibration simulations. The validation simulation yielded results that were comparable (RMSDs less than 1.0° and 0.3 cm for the rotational and translational kinematics, respectively) to those obtained from the calibration simulations. This study demonstrated the suitability of the proposed framework for performing future predictive simulations of sprinting, and gives confidence in its use to assess the cause-effect relationships of technique modification in relation to performance. Furthermore, this is the first study to provide dynamically consistent three-dimensional muscle-driven simulations of sprinting across different phases.

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Single-Leg Jump Performance Before and After Exercise in Healthy and Anterior Cruciate Ligament Reconstructed Individuals

Journal of Sport Rehabilitation ◽

10.1123/jsr.2019-0159 ◽

2020 ◽

Vol 29 (7) ◽

pp. 879-885

Author(s):

Haley Bookbinder ◽

Lindsay V. Slater ◽

Austin Simpson ◽

Jay Hertel ◽

Joseph M. Hart

Keyword(s):

Anterior Cruciate Ligament ◽

Repeated Measures ◽

Contact Time ◽

Cruciate Ligament ◽

Ground Contact ◽

Jump Height ◽

Before And After ◽

Healthy Control ◽

Ground Contact Time ◽

Anterior Cruciate

Context: Many clinicians measure lower-extremity symmetry after anterior cruciate ligament reconstruction (ACLR); however, testing is completed in a rested state rather than postexercise. Testing postexercise may better model conditions under which injury occurs. Objective: To compare changes in single-leg performance in healthy and individuals with history of ACLR before and after exercise. Design: Repeated-measures case-control. Setting: Laboratory. Patients: Fifty-two subjects (25 control and 27 ACLR). Intervention: Thirty minutes of exercise. Main Outcome Measures: Limb symmetry and involved limb performance (nondominant for healthy) for single-leg hop, ground contact time, and jump height during the 4-jump test. Cohen d effect sizes were calculated for all differences identified using a repeated-measures analysis of variance. Results: Healthy controls hopped farther than ACLR before (d = 0.65; confidence interval [CI], 0.09 to 1.20) and after exercise (d = 0.60; CI, 0.04 to 1.15). Those with ACLR had longer ground contact time on the reconstructed limb compared with the uninvolved limb after exercise (d = 0.53; CI, −0.02 to 1.09), and the reconstructed limb had greater ground contact time compared with the healthy control limb after exercise (d = 0.38; CI, −0.21 to 0.73). ACLR were less symmetrical than healthy before (d = 0.38; CI, 0.17 to 0.93) and after exercise (d = 0.84; CI, 0.28 to 1.41), and the reconstructed limb demonstrated decreased jump height compared with the healthy control limbs before (d = 0.75; CI, 0.19 to 1.31) and after exercise (d = 0.79; CI, 0.23 to 1.36). Conclusions: ACLR became more symmetric, which may be from adaptations of the reconstructed limb after exercise. Changes in performance and symmetry may provide additional information regarding adaptations to exercise after reconstruction.

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Sacral acceleration can predict whole-body kinetics and stride kinematics across running speeds

10.31236/osf.io/9vhwd ◽

2021 ◽

Author(s):

Ryan Alcantara ◽

Evan Day ◽

Michael Hahn ◽

Alena Grabowski

Keyword(s):

Risk Factors ◽

Contact Time ◽

Injury Risk ◽

Stress Fractures ◽

Whole Body ◽

Accelerometer Data ◽

Ground Contact ◽

Wearable Sensor ◽

Ground Contact Time ◽

Injury Risk Factors

Background. Stress fractures are injuries caused by repetitive loading during activities such as running. The application of advanced analytical methods such as machine learning to data from multiple wearable sensors has allowed for predictions of biomechanical variables associated with running-related injuries like stress fractures. However, it is unclear if data from a single wearable sensor can accurately estimate variables that characterize external loading during running such as peak vertical ground reaction force (vGRF), vertical impulse, and ground contact time. Predicting these biomechanical variables with a single wearable sensor could allow researchers, clinicians, and coaches to longitudinally monitor biomechanical running-related injury risk factors without expensive force-measuring equipment.Purpose. We quantified the accuracy of applying quantile regression forest (QRF) and linear regression (LR) models to sacral-mounted accelerometer data to predict peak vGRF, vertical impulse, and ground contact time across a range of running speeds.Methods. Thirty-seven collegiate cross country runners (24 females, 13 males) ran on a force-measuring treadmill at 3.8 – 5.4 m/s while wearing an accelerometer clipped posteriorly to the waistband of their running shorts. We cross-validated QRF and LR models by training them on acceleration data, running speed, step frequency, and body mass as predictor variables. Trained models were then used to predict peak vGRF, vertical impulse, and contact time. We compared predicted values to those calculated from a force-measuring treadmill on a subset of data (n = 9) withheld during model training. We quantified prediction accuracy by calculating the root mean square error (RMSE) and mean absolute percentage error (MAPE).Results. The QRF model predicted peak vGRF with a RMSE of 0.150 body weights (BW) and MAPE ± SD of 4.27 ± 2.85%, predicted vertical impulse with a RMSE of 0.004 BW*s and MAPE of 0.80 ± 0.91%, and predicted contact time with a RMSE of 0.011 s and MAPE of 4.68 ± 3.00%. The LR model predicted peak vGRF with a RMSE of 0.139 BW and MAPE of 4.04 ± 2.57%, predicted vertical impulse with a RMSE of 0.002 BW*s and MAPE of 0.50 ± 0.42%, and predicted contact time with a RMSE of 0.008 s and MAPE of 3.50 ± 2.27%. There were no statistically significant differences between QRF and LR model prediction MAPE for peak vGRF (p = 0.549) or vertical impulse (p = 0.073), but the LR model’s MAPE for contact time was significantly lower than the QRF model’s MAPE (p = 0.0497).Conclusions. Our findings indicate that the QRF and LR models can accurately predict peak vGRF, vertical impulse, and contact time (MAPE < 5%) from a single sacral-mounted accelerometer across a range of running speeds. These findings may be beneficial for researchers, clinicians, or coaches seeking to monitor running-related injury risk factors without force-measuring equipment.

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