Development of a novel biofeedback system for the sprint start

This study developed and evaluated a novel concurrent biofeedback system for the sprint start. Previous studies have investigated sprint start biofeedback applications, but these have either not considered important kinematics, coaching implications or key motor learning principles. The biofeedback system was developed to convey rear knee angle information, obtained from 3D motion capture to novice participants as changes in the colour of an LED start line when they were in the “set” position. Based on initial user feedback, the system indicated whether the participants’ rear knee angles were within ± 2° of 130° (green) or not (red). A two-group experimental study was then employed to explore the acute responses of novices to the use of the biofeedback system during the sprint start. When exposed to biofeedback, the experimental group (EXP, n = 10) exhibited less deviation (4.0 ± 2.4°) from the target rear knee angle than they did in either a pre-test (11.9 ± 6.9°) or post-test (10.4 ± 4.4°) condition without biofeedback. The control group (CON, n = 10) with no biofeedback exhibited greater deviation from the target rear knee angle than the EXP group in all three condition blocks (pre-test = 21.8 ± 15.1°, no intervention = 15.6 ± 7.3°, post-test = 14.3 ± 6.5°) but the group × condition interaction effect was not significant (P = 0.210). The novel biofeedback system can be used to manipulate selected “set” position kinematics and has the potential to be incorporated with different input systems (e.g. inertial measurement units (IMUs)) or in longitudinal designs.

Energy Transformation on Vault in Elite Artistic Gymnastics: Comparisons between Simple and Difficult Tsukahara and Yurchenko Vaults

Performance on vault in artistic gymnastics depends on the difficulty and the execution quality of the performed vault. However, differences of kinetic energy between simple and difficult vaults remain elusive. Therefore, in this study, 48 Tsukahara and Yurchenko vaults, performed by 20 top-level gymnasts, were recorded with 3D-motion capture and the flux of translational (TKE), angular kinetic (AKE), potential (PE), and total energy were calculated and compared. Results revealed that upon initial springboard contact, almost all of the kinetic energy for Tsukahara vaults is comprised of TKE, whereas Yurchenko vaults were characterized by substantially less TKE, but far greater AKE (and similar PE). During springboard contact of Tsukahara vaults, AKE is increased (+70%) and thereafter mostly preserved during push off from the table (−6%). For Yurchenko vaults, AKE is preserved during springboard contact but reduced (−30%) in exchange for PE at push off. During the second flight phase of Yurchenko vaults, total energy was 10% higher than at initial springboard contact (Tsukahara: −1%). For vaults of increasing difficulty, 5.9% more AKE is needed for each additional 180° of longitudinal-axis rotation. This knowledge may help coaches evaluate athletes’ potential and focus training on appropriate physical and/or technical aspects of the vault performance.

Step-To-Step Kinematic Validation Between an Inertial Measurement Unit (IMU) 3D System, a Combined Laser+IMU System and Force Plates During a 50 M Sprint in a Cohort of Sprinters

The purpose was to compare step-by-step kinematics measured using force plates (criterion), an IMU only and a combined laser IMU system in well-trained sprinters. Fourteen male experienced sprinters performed a 50-m sprint. Step-by-step kinematics were measured by 50 force plates and compared with an IMU-3D motion capture system and a combined laser+IMU system attached to each foot. Results showed that step kinematics (step velocity, length, contact and flight times) were different when measured with the IMU-3D system, compared with force plates, while the laser+IMU system, showed in general the same kinematics as measured with force plates without a systematic bias. Based upon the findings it can be concluded that the laser+IMU system is as accurate in measuring step-by-step kinematics as the force plate system. At the moment, the IMU-3D system is only accurate in measuring stride patterns (temporal parameters); it is not accurate enough to measure step lengths (spatial) and velocities due to the inaccuracies in step length, especially at high velocities. It is suggested that this laser+IMU system is valid and accurate, which can be used easily in training and competition to obtain step-by step kinematics and give direct feedback of this information during training and competition.

User Experience Survey of Innovative Softwares in Evaluation of Industrial-Related Ergonomic Hazards: A Focus on 3D Motion Capture Assessment

This paper aims to present user experience survey results of innovative software assessment technologies available in the market aimed in evaluating risks of industrial-related ergonomic hazards. The scope covers industrial ergonomics softwares currently available for purchase where time-limited free trial is offered, particularly those that utilize 3D Motion Capture Assessment which relies on kinematic inputs aided by non-invasive computer technology and artificial intelligence, and makes use of pre-determined weightings based on biomechanical risk factors. In light of the inclusion criterion, six industrial ergonomics softwares were considered. User field trials were conducted during January to September 2020 among 10 Occupational Health Subject Matter Experts (OH SME) coming from seven oil and gas Group Companies. Each OH SME attended a product demonstration by the shortlisted software vendor, participated in software trial at their respective workplaces, and provided feedback on the software's usability by filling out a survey questionnaire. OH SME responses were then collected for further qualitative analyses. Three of the eligible softwares relied on photo snapshot capturing work activity where subsequent analysis is done through competent professional judgment of qualitative risk. Another three were dependent on 3D Motion Capture Assessment where upper and lower limb motions of employees are digitally captured, recorded, and analyzed. Two of the softwares utilized sensors attached to different parts of employee's body, while one relied on Android/Smartphone snapshot of work activity and analyzed by the software's algorithm. Analyses of OH SME feedback revealed majority of them (n = 7) preferred using 3D Motion Capture Assessment over professional judgment of qualitative risk as an effective tool in evaluation of industrial work-related ergonomic risks. 3D Motion Capture Assessment provided accurate measurements of employee joint postures and postural angles. The tool ensured consistency in risk scoring for a particular industrial-related work activity as the calculation is standardized. The tool's algorithm is aligned with globally accepted assessment tools in evaluating ergonomic risks which enhances its validity. OH SMEs have expressed concerns on use of Android/Smartphone in Critical Infrastructure and Coastal Protection Authority facilities, training time needed in learning the software, and repetitive use of motion sensors among different employees which may lead to personal hygiene issues. 3D Motion Capture Assessment is a novel ergonomics software tool that can be used in real-time and accurate evaluation of ergonomic risks arising from industrial work-related activities. It can replace observational assessment of a work activity that may be prone to professional judgment errors. However, more validation and reliability studies need to be done in future as well as determining association between ergonomics risk scores obtained from the software and prevalence of work-related musculoskeletal disorders.

Placement Recommendations for Single Kinect-Based Motion Capture System in Unilateral Dynamic Motion Analysis

Low-cost, portable, and easy-to-use Kinect-based systems achieved great popularity in out-of-the-lab motion analysis. The placement of a Kinect sensor significantly influences the accuracy in measuring kinematic parameters for dynamics tasks. We conducted an experiment to investigate the impact of sensor placement on the accuracy of upper limb kinematics during a typical upper limb functional task, the drinking task. Using a 3D motion capture system as the golden standard, we tested twenty-one Kinect positions with three different distances and seven orientations. Upper limb joint angles, including shoulder flexion/extension, shoulder adduction/abduction, shoulder internal/external rotation, and elbow flexion/extension angles, are calculated via our developed Kinect kinematic model and the UWA kinematic model for both the Kinect-based system and the 3D motion capture system. We extracted the angles at the point of the target achieved (PTA). The mean-absolute-error (MEA) with the standard represents the Kinect-based system’s performance. We conducted a two-way repeated measure ANOVA to explore the impacts of distance and orientation on the MEAs for all upper limb angles. There is a significant main effect for orientation. The main effects for distance and the interaction effects do not reach statistical significance. The post hoc test using LSD test for orientation shows that the effect of orientation is joint-dependent and plane-dependent. For a complex task (e.g., drinking), which involves body occlusions, placing a Kinect sensor right in front of a subject is not a good choice. We suggest that place a Kinect sensor at the contralateral side of a subject with the orientation around 30∘ to 45∘ for upper limb functional tasks. For all kinds of dynamic tasks, we put forward the following recommendations for the placement of a Kinect sensor. First, set an optimal sensor position for capture, making sure that all investigated joints are visible during the whole task. Second, sensor placement should avoid body occlusion at the maximum extension. Third, if an optimal location cannot be achieved in an out-of-the-lab environment, researchers could put the Kinect sensor at an optimal orientation by trading off the factor of distance. Last, for those need to assess functions of both limbs, the users can relocate the sensor and re-evaluate the functions of the other side once they finish evaluating functions of one side of a subject.

Comparison of 3D Hip Joint Kinematics in People with Asymptomatic Pronation of the Foot and Non-Pronation Controls

Background: The impact of asymptomatic pronation on proximal joints during motion has not been well understood, and research on it remains limited. Therefore, the current study determines the effect of asymptomatic pronation of the foot on hip joint kinematics during gait. Methods: Forty participants were recruited for the study (20 with asymptomatic pronated feet and 20 with non-pronated feet). Foot assessment was conducted by navicular drop and rear- foot angle tests. Hip joint kinematics were measured via MVN Xsens system 3D-motion capture from sagittal, frontal and transverse planes during gait. An independent t-test was used to identify differences in kinematic variables. Results: Both groups were similar in characteristics, and there were no significant differences between the groups in age (P = 0.674) and BMI (P = 0.459). However, there was a significant difference in arch height (P = 0.001) and rear-foot angle (P = 0.001). Our findings showed there were insignificant differences between the asymptomatic pronated foot and non- pronated foot control groups in hip joint kinematics of sagittal (P = 0.618), frontal (P = 0.276), and transverse (P = 0.337) planes during a full gait cycle. Conclusion: Patients with asymptomatic pronation of the foot and non-pronation of the foot showed similar movement patterns of hip kinematics in all three planes. The findings of the present study highlight the need for clinicians to consider foot alignment when examining patients with asymptomatic pronation of the foot and non-pronation of the foot.