Ground Contact Time Research Articles

Influence Of Knee Extensor Strength On Spatiotemporal Gait Parameters In Adults With Prader-willi Syndrome

Adults with Prader-Willi Syndrome (PWS) are at greater risk for falls, which may be due to impaired muscle and gait performance. PURPOSE: To compare spatiotemporal gait parameters between adults with and without PWS, and to explore associations between knee extensor strength and spatiotemporal gait parameters in adults with PWS. METHODS: 10 adults with PWS, and 10 controls with and 10 without obesity completed isometric knee extensor (KE) strength assessments and gait analyses. Strength outcomes included peak KE torque, and early and late KE rate of torque development (RTD). Gait outcomes included speed, step length, step width, double support time, cadence, and gait-stability ratio (GSR). Step length and width were normalized to height, and strength outcomes were normalized to lean mass. Gait and strength outcomes were compared between groups with one-way MANOVA, and post hoc tests were made using Tukey’s HSD. Associations between strength and gait outcomes were explored using 1-tailed Pearson and Spearman correlations in the group with PWS. RESULTS: Gait (Pillai’s Trace = 0.86, p = 0.01) and strength outcomes (Pillai’s Trace = 0.52, p = 0.01) differed between groups. Adults with PWS had shorter step length (p < 0.01), longer double support (p = 0.01), and slower gait speed (p = 0.02) compared with controls without obesity, and higher GSR compared with controls without obesity (p = 0.01) and with obesity (p = 0.04). Adults with PWS had less KE torque (p < 0.01), early (p < 0.01) and late (p < 0.001) RTD compared with controls without obesity; and less KE torque (p = 0.01), less early (p = 0.03) and late (p = 0.01) RTD. In adults with PWS, greater KE torque was associated with faster speed (rho = 0.57, p < 0.01), smaller step width (r = -0.62, p = 0.03), shorter double support time (r = -0.57, p = 0.04), and lower GSR (rho = -0.79, p < 0.01). Greater late RTD was associated a faster speed (rho = 0.79, p = 0.01), lower GSR (rho = -0.71, p = 0.01), and longer step length (rho = 0.71, p = 0.01). CONCLUSIONS: Adults with PWS have different spatiotemporal gait parameters compared with controls that contribute to slower gait speed and reduced mobility. Larger GSR may reflect an adaptive strategy to increase ground contact time and avoid dynamic portions of the gait cycle. Improving knee extensor function may be useful to increase gait performance in adults with PWS.

Determinants of Top Speed Sprinting: Minimum Requirements for Maximum Velocity

Faster top sprinting speeds require shorter ground contact times, larger vertical forces, and greater thigh angular velocities and accelerations. Here, a framework using fundamental kinematic and kinetic relationships is presented that explores the effect of body dimensions on these mechanical determinants of sprinting performance. The analysis is applied to three hypothetical runners of different leg lengths to illustrate how these mechanical determinants of speed vary with body dimensions. Specific attention is focused on how the following variables scale with leg length and top speed: ground contact time, step rate, step length, ratio of step length to leg length, ratio of vertical force to body weight, total thigh range of motion, average thigh angular velocity, and maximum thigh angular acceleration. The analysis highlights the inherent biological tradeoffs that interplay to govern the optimal dimensions for sprinting speed and underscores that accounting for leg length may facilitate interpretation in future investigations examining the relationship between these mechanical variables and top speed. Furthermore, for athletes with given body dimensions and sprinting performance goals, this framework could help to establish the minimum requirements for maximum velocity.

Kinetic Responses to External Cues Are Specific to Both the Type of Cue and Type of Exercise in Adolescent Athletes.

Barillas, SR, Oliver, JL, Lloyd, RS, and Pedley, J. Kinetic responses to external cues are specific to both the type of cue and type of exercise in adolescent athletes. J Strength Cond Res 37(3): 597-605, 2023-The purpose of this study was to examine how external cues influence kinetics during isometric and dynamic tasks in adolescent athletes. Fifteen adolescent male soccer players performed an isometric midthigh pull (IMTP), unloaded and loaded squat jumps (SJs) (15 and 30% of body mass), countermovement jump (CMJ), and drop jump (DJ) using a neutral or external force-specific or velocity-specific cues. Cue type had limited effects on outcomes in the IMTP or SJs, with mostly trivial ( g < 0.20), nonsignificant differences ( p > 0.05) across kinetic variables. In the CMJ and DJ, a force cue significantly ( p < 0.05) increased jump height ( g = 0.43 & 0.52) compared with a velocity cue, but in the DJ, a force cue significantly increased jump height ( g = 0.52) compared with both a neutral and velocity cue. However, a velocity cue significantly ( p < 0.05) reduced ground contact time ( g = 0.73-1.52) and time to peak force ( g = 0.50-1.29) in both the CMJ and DJ when compared with a force and neutral cue and increased force and power-related measures ( g = 0.33-1.12) in the CMJ and DJ when compared with a force cue. In adolescent athletes, the type of external cue had limited effects on kinetic measures in an IMTP and SJ but differential effects on both a CMJ and DJ, suggesting cues have more effect with increasing movement velocity. Consequently, practitioners working with adolescent athletes should consider both the type of exercise and the desired outcome when providing external cues.

The Impact of COVID-19 and Muscle Fatigue on Cardiorespiratory Fitness and Running Kinetics in Female Recreational Runners.

Background: There is evidence that fully recovered COVID-19 patients usually resume physical exercise, but do not perform at the same intensity level performed prior to infection. The aim of this study was to evaluate the impact of COVID-19 infection and recovery as well as muscle fatigue on cardiorespiratory fitness and running biomechanics in female recreational runners. Methods: Twenty-eight females were divided into a group of hospitalized and recovered COVID-19 patients (COV, n = 14, at least 14 days following recovery) and a group of healthy age-matched controls (CTR, n = 14). Ground reaction forces from stepping on a force plate while barefoot overground running at 3.3 m/s was measured before and after a fatiguing protocol. The fatigue protocol consisted of incrementally increasing running speed until reaching a score of 13 on the 6–20 Borg scale, followed by steady-state running until exhaustion. The effects of group and fatigue were assessed for steady-state running duration, steady-state running speed, ground contact time, vertical instantaneous loading rate and peak propulsion force. Results: COV runners completed only 56% of the running time achieved by the CTR (p < 0.0001), and at a 26% slower steady-state running speed (p < 0.0001). There were fatigue-related reductions in loading rate (p = 0.004) without group differences. Increased ground contact time (p = 0.002) and reduced peak propulsion force (p = 0.005) were found for COV when compared to CTR. Conclusion: Our results suggest that female runners who recovered from COVID-19 showed compromised running endurance and altered running kinetics in the form of longer stance periods and weaker propulsion forces. More research is needed in this area using larger sample sizes to confirm our study findings.

Loudness affects motion: asymmetric volume of auditory feedback results in asymmetric gait in healthy young adults

BackgroundThe potential of auditory feedback for motor learning in the rehabilitation of various diseases has become apparent in recent years. However, since the volume of auditory feedback has played a minor role so far and its influence has hardly been considered, we investigate the volume effect of auditory feedback on gait pattern and gait direction and its interaction with pitch.MethodsThirty-two healthy young participants were randomly divided into two groups: Group 1 (n = 16) received a high pitch (150-250 Hz) auditory feedback; group 2 (n = 16) received a lower pitch (95-112 Hz) auditory feedback. The feedback consisted of a real-time sonification of the right and left foot ground contact. After an initial condition (no auditory feedback and full vision), both groups realized a 30-minute habituation period followed by a 30-minute asymmetry period. At any condition, the participants were asked to walk blindfolded and with auditory feedback towards a target at 15 m distance and were stopped 5 m before the target. Three different volume conditions were applied in random order during the habituation period: loud, normal, and quiet. In the subsequent asymmetry period, the three volume conditions baseline, right quiet and left quiet were applied in random order.ResultsIn the habituation phase, the step width from the loud to the quiet condition showed a significant interaction of volume*pitch with a decrease at high pitch (group 1) and an increase at lower pitch (group 2) (group 1: loud 1.02 ± 0.310, quiet 0.98 ± 0.301; group 2: loud 0.95 ± 0.229, quiet 1.11 ± 0.298). In the asymmetry period, a significantly increased ground contact time on the side with reduced volume could be found (right quiet: left foot 0.988 ± 0.033, right foot 1.003 ± 0.040, left quiet: left foot 1.004 ± 0.036, right foot 1.002 ± 0.033).ConclusionsOur results suggest that modifying the volume of auditory feedback can be an effective way to improve gait symmetry. This could facilitate gait therapy and rehabilitation of hemiparetic and arthroplasty patients, in particular if gait improvement based on verbal corrections and conscious motor control is limited.

Greater Breast Support Is Associated With Reduced Oxygen Consumption and Greater Running Economy During a Treadmill Running Task.

IntroductionBreast pain is a major barrier to running for women. While breast support through the use of sports bras reduces breast-related discomfort, the effect of breast support on running performance is less understood. Therefore, the purpose of the current study was to evaluate the effect of greater breast support on oxygen consumption and running economy during a treadmill running task.MethodsFifteen female recreational runners performed a 10-min treadmill running task at their preferred running speed in each of two sports bra conditions: low support and high support. Participants ran on an instrumented treadmill (1,200 Hz, Bertec) while indirect calorimetry was performed using a metabolic measurement system (100 Hz, TrueOne, ParvoMedics). Average VO2 (absolute and relative) from the third to 10th minutes was used to evaluate oxygen consumption. Running economy was calculated as the distance traveled per liter of oxygen consumed. Paired samples t-tests were used to compare mean oxygen consumption and running economy values between breast support conditions. Correlation analysis was performed to evaluate the relationship between breast size and change in running performance.ResultsGreater breast support was associated with reductions in absolute (p < 0.001) and relative oxygen consumption (p < 0.001; LOW: 30.9 ± 7.1 ml/kg/min; HIGH: 28.7 ± 6.7 ml/kg/min). Greater breast support was associated with increases in running economy (p < 0.001; LOW: 88.6 ± 29.1 m/L O2; HIGH: 95.2 ± 31.1 m/L O2). No changes in temporospatial characteristics of running were observed including cadence (p = 0.149), step length (p = 0.300) or ground contact time (p = 0.151). Strong positive linear correlations were observed between the change in running performance metrics and breast size (Oxygen Consumption: p < 0.001, r = 0.770; Relative Oxygen Consumption: p < 0.001, r = 0769; Running Economy: p < 0.001, r = 0.807).ConclusionsGreater breast support was associated with reduced oxygen consumption and increased running economy. These findings demonstrate that greater breast support is not only associated with improved comfort but also improved running performance.

The effect of two types of ankle orthoses on the repetitive rebound jump performance

BackgroundAnkle orthotics decreases the maximal vertical jump height. It is essential to maximize jump height and minimize ground contact time during athletic performance. However, the effect of ankle orthotics on athletic performance has not been reported. We aimed to investigate the effect of ankle orthotics on squat jump (SJ), countermovement jump (CMJ), and repetitive rebound jump (RJ) performance.MethodsTwenty healthy volunteers performed SJ, CMJ, repetitive RJ under no-orthosis and two orthotic conditions (orthosis 1 and orthosis 2). During SJ and CMJ, we measured the vertical ground reaction force and calculated the following parameters: jump height, peak vertical ground reaction force, rate of force development, net vertical impulse, and peak power. During repetitive RJ, the jump height, contact time, and RJ index were measured. A two-dimensional motion analysis was used to quantify the ankle range of motion in the sagittal plane during SJ, CMJ, and repetitive RJ.ResultsMultivariate analysis of variance and the post hoc test showed orthosis 2 significantly decreased in the vertical jump height (p = 0.003), peak power (p = 0.007), and maximum plantarflexion and dorsiflexion angles (p < 0.001) during SJ Ankle orthoses 1 and 2 did not influence to the RJ performance compared to those using the no-orthosis condition. Additionally, orthosis 2 significantly decreased the jump height at the end of repetitive RJ (p = 0.046).ConclusionsThese results suggest that ankle orthosis do not affect average RJ performance but should be considered when performing repetitive jumps frequently.

Ground Contact Time Estimating Wearable Sensor to Measure Spatio-Temporal Aspects of Gait.

Inpatient gait analysis is an essential part of rehabilitation for foot amputees and includes the ground contact time (GCT) difference of both legs as an essential component. Doctors communicate improvement advice to patients regarding their gait pattern based on a few steps taken at the doctor’s visit. A wearable sensor system, called Suralis, consisting of an inertial measurement unit (IMU) and a pressure measuring sock, including algorithms calculating GCT, is presented. Two data acquisitions were conducted to implement and validate initial contact (IC) and toe-off (TO) event detection algorithms as the basis for the GCT difference determination for able-bodied and prosthesis wearers. The results of the algorithms show a median GCT error of −51.7 ms (IMU) and 14.7 ms (sensor sock) compared to the ground truth and thus represent a suitable possibility for wearable gait analysis. The wearable system presented, therefore, enables a continuous feedback system for patients and, above all, a remote diagnosis of spatio-temporal aspects of gait behaviour based on reliable data collected in everyday life.

EFFECT OF OUTSOLE THICKNESS ON RUNNING BIOMECHANICS

Running shoes with increased or decreased sole thickness are postulated to improve running performance, besides to protect runners against high impact forces and running injuries. However, there is no evidence showing that running shoe developments emerging on the market help tackle running injuries. In this study, we compared the effect of different outsole thicknesses: (i) barefoot, (ii) minimalist and (iii) maximalist sports shoes on running biomechanics. Fifteen male subjects (age 23.19 ± 0.73 years old) who had regular exercises for at least 75 minutes per week were recruited to participate in this study. Participants had completed three minutes of running on a treadmill in each condition. Lower extremity kinetics and kinematics were analysed. There was no difference between maximalist running shoes and minimalist running shoes with respect to maximum vertical ground reaction force (VGRF) (p = 0.221), step length (p = 0.50) and cadence (p = 0.30). In addition, we observed longer ground contact time in maximalist running shoes (1.087 ± 0.115 s) when compared with minimalist running shoes (1.051 ± 0.105 s) (p = 0.007). On the other hand, runners had significantly higher knee flexion and adduction in minimalist shoes than maximalist shoes (p = 0.046). In conclusion, running in minimalist shoes, at least in a short period, produces greater running efficiency with shorter ground contact time but may result in a higher injury risk at the knee joint.

Energy Cost of Running in Well-Trained Athletes: Toward Slope-Dependent Factors

This study aimed to determine the contribution of metabolic, cardiopulmonary, neuromuscular, and biomechanical factors to the energy cost (ECR) of graded running in well-trained runners. Eight men who were well-trained trail runners (age: 29 [10]y, mean [SD]; maximum oxygen consumption: 68.0 [6.4]mL·min-1·kg-1) completed maximal isometric evaluations of lower limb extensor muscles and 3 randomized trials on a treadmill to determine their metabolic and cardiovascular responses and running gait kinematics during downhill (DR: -15% slope), level (0%), and uphill running (UR: 15%) performed at similar O2 uptake (approximately 60% maximum oxygen consumption). Despite similar O2 demand, ECR was lower in DR versus level running versus UR (2.5 [0.2] vs 3.6 [0.2] vs 7.9 [0.5]J·kg-1·m-1, respectively; all P < .001). Energy cost of running was correlated between DR and level running conditions only (r2 = .63; P = .018). Importantly, while ECR was correlated with heart rate, cardiac output, and arteriovenous O2 difference in UR (all r2 > .50; P < .05), ECR was correlated with lower limb vertical stiffness, ground contact time, stride length, and step frequency in DR (all r2 > .58; P < .05). Lower limb isometric extension torques were not related to ECR whatever the slope. The determining physiological factors of ECR might be slope specific, mainly metabolic and cardiovascular in UR versus mainly neuromuscular and mechanical in DR. This possible slope specificity of ECR during incline running opens the way for the implementation of differentiated physiological evaluations and training strategies to optimize performance in well-trained trail runners.

Applying augmented feedback in basketball training facilitates improvements in jumping performance

ABSTRACT Augmented feedback, which is feedback about movement characteristics provided by an external source, can facilitate performance improvements. Results from recent studies, in which information about the jumping height were presented, indicated increased jumping performance due to augmented feedback. In the present study we aimed to utilize augmented feedback about the jumping height in regular basketball training. Therefore, augmented feedback was implemented and part of the training regime, and information about the jumping height was displayed while subjects performed catch and shoot exercises with the basketball. 18 subjects (9 with augmented feedback, 9 without augmented feedback) practiced for 3 weeks (9 training sessions). The subjects receiving augmented feedback, but not subjects in the control group, displayed increased jumping heights of countermovement-jumps and drop-jumps after the training. The ground contact times of countermovement-jumps and drop-jumps were not significantly changed after training. The number of successful hits, indicating ball performance, did also not change after training. Thus augmented feedback had no detrimental effect on sport-specific performance. The unchanged ground contact times of drop-jumps in combination with increased jumping heights indicate increased efficiency of stretch shortening cycle contractions. According to the positive effect of augmented feedback on jumping performance and the simplicity with which it was integrated into the training regime we recommend this method for regular basketball training. Highlights Augmented feedback about the jumping height in basketball training facilitated jumping height of countermovement-jumps and drop-jumps. The ground contact times were not altered, suggesting increased efficiency of the stretch-shortening cycle during jumping. According to the positive effect and its simple implementation augmented feedback is recommended for regular basketball training.

The association between reactive strength index and reactive strength index modified with approach jump performance.

Jumping performance is one of the key components of volleyball game, thus evaluating jumping ability through different biomechanical variables offers opportunity for performance optimization. The aim of this study was to assess the associations between reactive strength index (RSI), reactive strength index modified (RSImod) and approach jump performance in male volleyball players. Forty volleyball players performed drop jump (DJ) form 40 cm high box, bilateral and unilateral countermovement jumps (CMJ) and approach jump. RSI in DJ was calculated as the ratio between jump height and ground contact time, while the RSI in CMJ tasks (RSImod) was calculated as ratio between jump height and jump time. Our results indicate that the relationships among different RSI variants and approach jump in volleyball players are moderate to strong (r = 0.42–0.73), with the highest correlations being observed for RSImod from bilateral CMJ (r = 0.676–0.727). Those observations are in line with the principle of movement specificity, which suggests that the best performance indicator should be the task that best resembles the demands of the sport-specific movements. Further research is needed to reveal more about the potential of implementing these findings for training optimization through monitoring RSI and RSImod values.

The Effectiveness of Gait Retraining on Running Kinematics, Kinetics, Performance, Pain, and Injury in Distance Runners: A Systematic Review With Meta-analysis.

To evaluate the effectiveness of running gait retraining on kinematics, kinetics, performance, pain, and injury in distance runners. Intervention systematic review with meta-analysis. Seven electronic databases from inception to March 2021. Randomized controlled trials that (1) evaluated running gait retraining compared to no intervention, usual training, placebo, or standard care and (2) reported biomechanical, physiological, performance, or clinical outcomes. Random-effects metaanalyses were completed, and the certainty of evidence was judged using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. We categorized interventions into step rate, non-rearfoot footstrike, impact, ground contact time, and multiparameter subgroups. We included 19 trials (673 participants). Moderate-certainty evidence indicated step rate gait retraining increased step rate (SMD 1.03 [95% confidence interval {CI}: 0.63, 1.44]; number of trials (N): 4; I2: 0%) and reduced average vertical loading rate (SMD -0.57 [95% CI, -1.05 to -0.09], N: 3; I2: 0%). Low-certainty evidence indicated non-rearfoot footstrike retraining increased knee flexion at initial contact (SMD 0.74 [95% CI, 0.11 to 1.37]; N: 2; I2: 0%), but did not alter running economy (SMD 0.21 [95% CI, -1.11 to 1.52]; N: 3; I2: 19%).). Low-certainty evidence indicated multiparameter retraining did not alter running economy (SMD 0.32 [-0.39, 1.02]; N: 3; I2: 19%) or performance (SMD 0.14 [95% CI, -4.87 to 4.58]; N: 2; I2: 18%). Insufficient trials reported on pain outcomes. Two trials demonstrated reduced 1-year injury incidence following gait retraining. Gait retraining interventions altered step rate and knee kinematics, lowered vertical loading rates, and did not affect running performance. J Orthop Sports Phys Ther 2022;52(4):192-206. Epub 05 Feb 2022. doi:10.2519/jospt.2022.10585.

Reliability, Validity, and Performance Characteristics of Elite Adolescent Athletes at Different Stages of Maturity in the 10 to 5 Repeated Jump Test.

To examine the reliability, validity, and performance characteristics of the 10 to 5 repeated jump test (10-5 RJT) in adolescent male athletes. The 10-5 RJT has been shown to be a valid and reliable test of reactive strength index (RSI) in older adolescents (age 17-19y), but less is known in younger adolescent athletes at different stages of maturity. Athletes (age 11-17y) completed the 10-5 RJT on 2 days, 1 week apart, to examine the reliability (n = 41), validity (n = 18) of the test. Athletes were classified as pre, circa, or post peak height velocity (PHV) height velocity using maturity offset to examine the effect of maturation status on RSI, flight time (FT), ground contact time (GCT), and jump height (JH) (n = 68) using a cross-sectional design. Paired samples t tests showed no significant differences (P ≥ .05), and Bland-Altman analysis showed no bias and close limits of agreement for RSI, JH, FT, and GCT between the contact mat and force plate. Interday reliability was rated excellent for RSI (intraclass correlation coefficient = .91) and good for GCT, FT, and JH (intraclass correlation coefficient = .81-.85). All variables had a coefficient of variation ≤ 10%. RSI increased across maturation groups, with significant differences between pre-PHV and post-PHV groups (P = .014, d = 1.00). The 10-5 RJT is a valid and reliable test for adolescent male athletes. Greater RSI with advancing maturity was primarily due to increased FT and JH, with GCT remaining similar.

The Chronic Effects of a Quantified Jump-Landing Program on Bone Health, Body Composition and Performance Parameters in Premenopausal Women

The primary purpose of this study was to determine the effects of a 12-month quantified jump-landing program at clinically relevant bone sites in premenopausal women. Secondary measures of interest included; lower body explosive power, muscle reactivity, balance performance parameters and body composition. A longitudinal controlled trial was implemented to determine the effect of utilizing previously quantified jumps and hops with specific cues provided for jump-landings. Participants; Fifty-seven women (age, 42.4 ± 5.50 y; body mass, 70.2 ± 11.5 kg; height, 165.4 ± 0.10 cm; body fat, 31.5 ± 6.20%) were assigned to a jump (JL) or control (CON) group. The JL performed periodized jumping-landing exercises up to five times per week for 12-months. Linear mixed model regression analysis was used to determine if differences existed between the JL and CON. Significant group main effects (P&lt;0.01) in favour of the JL (↑0.41 - ↑3.72%) were observed for bone mineral density and bone mineral content at the femoral neck, total hip and lumbar spine. Significant group main effects (P&lt;0.01) for cross-sectional area, cortical thickness and section modulus at the femoral narrow neck were also in favour of the JL (↑2.78 - ↑3.84%). For ground contact time, improvements in the JL over the CON between baseline and 12-months were apparent (↑21.9% vs. ↓8.86%) with significant group and time effects (P&lt;0.01) being observed. A longitudinal quantified periodized jumplanding program performed 2-3 mins/day; 4-5 times a week is osteogenically effective in improving bone strength at clinically relevant lower body sites associated with osteoporosis in premenopausal women.

A Single Sacral-Mounted Inertial Measurement Unit to Estimate Peak Vertical Ground Reaction Force, Contact Time, and Flight Time in Running.

Peak vertical ground reaction force (), contact time (), and flight time () are key variables of running biomechanics. The gold standard method (GSM) to measure these variables is a force plate. However, a force plate is not always at hand and not very portable overground. In such situation, the vertical acceleration signal recorded by an inertial measurement unit (IMU) might be used to estimate , , and . Hence, the first purpose of this study was to propose a method that used data recorded by a single sacral-mounted IMU (IMU method: IMUM) to estimate . The second aim of this study was to estimate and using the same IMU data. The vertical acceleration threshold of an already existing IMUM was modified to detect foot-strike and toe-off events instead of effective foot-strike and toe-off events. Thus, and estimations were obtained instead of effective contact and flight time estimations. One hundred runners ran at 9, 11, and 13 km/h. IMU data (208 Hz) and force data (200 Hz) were acquired by a sacral-mounted IMU and an instrumented treadmill, respectively. The errors obtained when comparing , , and estimated using the IMUM to , , and measured using the GSM were comparable to the errors obtained using previously published methods. In fact, a root mean square error (RMSE) of 0.15 BW (6%) was obtained for while a RMSE of 20 ms was reported for both and (8% and 18%, respectively). Moreover, even though small systematic biases of 0.07 BW for and 13 ms for and were reported, the RMSEs were smaller than the smallest real differences [: 0.28 BW (11%), : 32.0 ms (13%), and : 32.0 ms (30%)], indicating no clinically important difference between the GSM and IMUM. Therefore, these results support the use of the IMUM to estimate , , and for level treadmill runs at low running speeds, especially because an IMU has the advantage to be low-cost and portable and therefore seems very practical for coaches and healthcare professionals.

Role of Antigravity Training in Rehabilitation and Return to Sport After Running Injuries

AbstractAnti-gravity treadmill training is a therapeutic option to help recovering runners return to activity after injury. This current concept paper provides a synopsis of the latest evidence of the biomechanical and metabolic changes that occur with body weight support (BWS) treadmill training, effects of antigravity treadmill training on clinical outcomes and clinical case studies in injured runners. Literature searches identified studies with descriptive, experimental and interventional designs and case studies that examined acute and chronic use of antigravity treadmills in runners and relevant populations. Laboratory-based studies were included to provide technical considerations for rehabilitation programming. Antigravity treadmills use causes reductions in cadence, ground reaction forces (GRF), GRF impulses, knee and ankle range of motion, and vertical stiffness, with elevations in stride duration, flight time, ground contact time, and plantarflexion. Antigravity treadmills appear useful across a spectrum of injuries in runners, including postsurgical repair of osteochondral defect, stress reactions (medial tibia, pelvis), and lumbar disc herniation. Runners may preserve aerobic fitness, muscle activation patterns, and muscle mass during recovery compared to traditional rehabilitation protocols. Technical considerations for accurate loading include treadmill frame adjustment to appropriate height to ensure accuracy of level of BWS while running, and monitoring for fast cadence to ensure impact loading rates remain low. Speed or grade can be increased to maintain metabolic demand and fitness while minimizing bone and tissue loading. Monitoring for symptom provocation will guide protocol adjustments to BWS and prescriptions. Once able to run pain-free (sustained or interval) >95% BWS for >30 min, the runner is likely ready to safely transition to ground running. Antigravity treadmill training can be considered when available to facilitate smooth transition back to ground running in a conditioned state.

Ground reaction force measurement during running using insoles with MEMS six-axis force sensors.

In this study, the forces applied to the sole during walking, jogging, and running were evaluated using Shokkaku-shoes that are equipped with MEMS 6-axis force sensors and acceleration/gyro sensors in their insoles. The MEMS 6-axis force sensors were placed at the thenar, the hypothenar, and the heel, and the acceleration/gyro sensor was placed at the center of the sole. Measurements were conducted on an athletics track over approximately 30 m for each movement. The data were analyzed for the three axial forces at the thenar, the hypothenar, and the heel. Then, it was found that the vertical forces in the forefoot increased as the motion became close to running, and the ground contact time gradually became shorter. Only braking forces were observed in walking, and propulsive force was detected only in the jogging and running motion unlike the typical GRF measurements using force plates.

Evaluation of lower extremity gait analysis using Kinect V2® tracking system.

Introduction: Microsoft Kinect V2® (Kinect) is a peripheral device of Xbox® and acquires information such as depth, posture, and skeleton definition. In this study, we investigated whether Kinect can be used for human gait analysis. Methods: Ten healthy volunteers walked 20 trials, and each walk was recorded by a Kinect and infrared- and marker-based-motion capture system. Pearson’s correlation and overall agreement with a method of meta-analysis of Pearson’s correlation coefficient were used to assess the reliability of each parameter, including gait velocity, gait cycle time, step length, hip and knee joint angle, ground contact time of foot, and max ankle velocity. Hip and knee angles in one gait cycle were calculated in Kinect and motion capture groups. Results: The coefficients of correlation for gait velocity (r = 0.92), step length (r = 0.81) were regarded as strong reliability. Gait cycle time (r = 0.65), minimum flexion angle of hip joint (r = 0.68) were regarded as moderate reliability. The maximum flexion angle of the hip joint (r = 0.43) and maximum flexion angle of the knee joint (r = 0.54) were regarded as fair reliability. Minimum flexion angle of knee joint (r = 0.23), ground contact time of foot (r = 0.23), and maximum ankle velocity (r = 0.22) were regarded as poor reliability. The method of meta-analysis revealed that participants with small hip and knee flexion angles tended to have poor correlations in maximum flexion angle of hip and knee joints. Similar trajectories of hip and knee angles were observed in Kinect and motion capture groups. Conclusions: Our results strongly suggest that Kinect could be a reliable device for evaluating gait parameters, including gait velocity, gait cycle time, step length, minimum flexion angle of the hip joint, and maximum flexion angle of the knee joint.

ACUTE EFFECT OF WHOLE-BODY VIBRATION COMBINED WITH STATIC STRETCHING ON FEMALE GYMNASTS’ LEG AND VERTICAL STIFFNESS DURING RUNNING

&lt;p&gt;Although whole-body vibration (WBV) combined with static stretching (SS) have proven a suitable method to enhance flexibility without losing muscular strength, it is still unknown what its effect are on running mechanics. Therefore, the purpose of the study was to examine the effect of a WBV combined with SS (WBVSS) warm up procedure on lower limb stiffness and spatiotemporal variables during running. Twenty-two female gymnasts performed 30-s running bouts at 4.44 m.s-1 on a treadmill before and after a WBVSS intervention stimulus. The WBVSS stimulus included two sets of 20s of SS of four different muscle groups on the vibration platform. Leg and vertical stiffness values were calculated using a spring mass model. The results showed a statistically significant interaction effect on vertical stiffness (Kvert), leg stiffness (Kleg), change in leg length (ΔL), maximal ground reaction force (Fmax), contact time (Tc), and flight time (Tf). Results indicated that, a warm-up including SS combined with WBV did not produce significant effect on mean values of Kleg and Kvert, and related kinetic and kinematic variables.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;&lt;p&gt;&lt;strong&gt; Article visualizations:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;img src="/-counters-/edu_01/0994/a.php" alt="Hit counter" /&gt;&lt;/p&gt;