Validity and reliability of an accelerometer-based player tracking device

<div><p>This study aimed to determine the intra- and inter-device accuracy and reliability of wearable athletic tracking devices, under controlled laboratory conditions. A total of nineteen portable accelerometers (Catapult OptimEye S5) were mounted to an aluminum bracket, bolted directly to an Unholtz Dickie 20K electrodynamic shaker table, and subjected to a series of oscillations in each of three orthogonal directions (front-back, side to side, and up-down), at four levels of peak acceleration (0.1g, 0.5g, 1.0g, and 3.0g), each repeated five times resulting in a total of 60 tests per unit, for a total of 1140 records. Data from each accelerometer was recorded at a sampling frequency of 100Hz. Peak accelerations recorded by the devices, Catapult PlayerLoad™, and calculated player load (using Catapult’s Cartesian formula) were used for the analysis. The devices demonstrated excellent intradevice reliability and mixed interdevice reliability. Differences were found between devices for mean peak accelerations and PlayerLoad™ for each direction and level of acceleration. Interdevice effect sizes ranged from a mean of 0.54 (95% CI: 0.34–0.74) (small) to 1.20 (95% CI: 1.08–1.30) (large) and ICCs ranged from 0.77 (95% CI: 0.62–0.89) (very large) to 1.0 (95% CI: 0.99–1.0) (nearly perfect) depending upon the magnitude and direction of the applied motion. When compared to the player load determined using the Cartesian formula, the Catapult reported PlayerLoad™ was consistently lower by approximately 15%. These results emphasize the need for industry wide standards in reporting validity, reliability and the magnitude of measurement errors. It is recommended that device reliability and accuracy are periodically quantified.</p></div

RELATIONSHIP BETWEEN KINEMATIC CHARACTERISTICS AND FREE-THROW SHOOTING PRECISION: MARKERLESS MOTION CAPTURE ANALYSIS

The search for aspects of basketball shooting that characterize successful performance is an area of focus for sports biomechanists. However, the systematic evaluation of these key elements during shooting practice is limited due to the time it takes to collect and/or process the data. Thus, the purpose of the present study was to evaluate the relationship between some of the key kinematic variables extracted from a markerless motion capture system on free-throw shot performance. Multivariable linear regression analysis indicated that shot plane alignment, trunk rotation, entry angle, and timing of elbow extension were some of the key contributors to free-throw shot precision. Overall, these kinematic variables serve as a preliminary set of outcomes that can be reported to coaches and players that decide to use markerless motion capture technology for free-throw shooting biomechanical analysis

Identifying special operative trainees at-risk for musculoskeletal injury using full body kinematics

Introduction: Non-combat musculoskeletal injuries (MSKIs) during military training significantly impede the US military’s functionality, with an annual cost exceeding $3.7 billion. This study aimed to investigate the effectiveness of a markerless motion capture system and full-body biomechanical movement pattern assessments to predict MSKI risk among military trainees.Methods: A total of 156 male United States Air Force (USAF) airmen were screened using a validated markerless biomechanics system. Trainees performed multiple functional movements, and the resultant data underwent Principal Component Analysis and Uniform Manifold And Projection to reduce the dimensionality of the time-dependent data. Two approaches, semi-supervised and supervised, were then used to identify at-risk trainees.Results: The semi-supervised analysis highlighted two major clusters with trainees in the high-risk cluster having a nearly five times greater risk of MSKI compared to those in the low-risk cluster. In the supervised approach, an AUC of 0.74 was produced when predicting MSKI in a leave-one-out analysis.Discussion: The application of markerless motion capture systems to measure an individual’s kinematic profile shows potential in identifying MSKI risk. This approach offers a novel way to proactively address one of the largest non-combat burdens on the US military. Further refinement and wider-scale implementation of these techniques could bring about substantial reductions in MSKI occurrence and the associated economic costs

Mais é menos? O impacto do Projeto 6º Ano Experimental – SME/RJ

The aim of this study is to assess the short-term impact of the sixth-grade experimental project and the factors that mediate this impact. The main feature of the project proposed by the Department of Municipal Education (SME) of Rio de Janeiro, in 2011, is its expansion up to the 6th grade the elementary education, with only one lead teacher to teach the main subjects. To evaluate the project, we used the differences-in-differences method with propensity scorematching. The results indicate an improvement of 0.16 standard deviations in mathematics at the end of the first half of the project, for the schools that entered in the 6th Grade Experimental, in 2014. The main mechanisms that explain performance improvement are the improved climate in the classroom, in pedagogical autonomy and in the training of teachers.O objetivo deste estudo é avaliar o impacto de curto prazo do Projeto 6º Ano Experimental e os fatores que mediam esse impacto. Proposto pela Secretaria Municipal de Educação do Rio de Janeiro em 2011, sua principal característica é a ampliação para seis anos do primeiro ciclo do ensino fundamental, com a presença de um único professor-regente lecionando as principais disciplinas. Para avaliar o projeto, foi utilizado o método de diferenças-em-diferenças com pré-pareamento por escore de propensão. Os resultados indicam melhora de 0,16 desvios-padrão para Matemática ao final do primeiro semestre do projeto, para as escolas que ingressaram no 6º Ano Experimental em 2014. Os principais mecanismos que explicam o aumento de desempenho são a melhora no clima em sala de aula, na autonomia pedagógica e na capacitação dos professores.El objetivo de este estudio es evaluar el impacto de corto plazo del Proyecto 6º Año Experimental y los factores mediadores en dicho impacto. Propuesto por la Secretaría Municipal de Educación de Rio de Janeiro en 2011, su principal característica es la ampliación para seis años del primer ciclo de la educación fundamental, con la presencia de tan solo un profesor-regente impartiendo las principales asignaturas. Para evaluar el proyecto se utilizó el método de diferencias-en-diferencias con pre pareado por escore de propensión. Los resultados indican una mejora de 0,16 desviaciones estándar para Matemáticas a fines del primer semestre del proyecto, para las escuelas que ingresaron en el 6º Año Experimental en 2014. Los principales mecanismos que explican el aumento de desempeño son la mejora del clima en el aula, en la autonomía pedagógica y en la capacitación de los profesores

Mean catapult PlayerLoad™ (PL) from five repeats with 95% confidence intervals.

<p>For clarity only 5 devices are shown (3g peak acceleration, 8 Hz). Please see Supporting Information for complete data set (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191823#pone.0191823.s001" target="_blank">S1 Data</a>).</p

Peak acceleration interdevice effect sizes (Cohen’s d).

<p>Peak acceleration interdevice effect sizes (Cohen’s d).</p

Descriptive statistics: 3.0 g, 8 Hz applied peak acceleration.

<p>Data for 0.1g, 0.5g and 1.0g applied acceleration can be found in the Supporting Information.</p