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Tatiana Tapajcikova, Dávid Líška, Ladislav Batalik, Clea P. Tucker, and Alena Kobesova

High-quality sensory perception and body scheme (somatognosis) are important aspects for sport performance. This study compares stereognosis, body scheme, and kinesthesia in a group of 36 competitive karate athletes against a control group of 32 general population participants. The stereognosis Petrie test, two body scheme tests, and three kinesthesia tests served as outcome measurement tools. No significant difference was found in the stereognosis Petrie test, for the dominant (p = .389) or the nondominant (p = .791) hand, nor in the kinesthesia test (dominant, p = .661 and nondominant, p = .051). Karate athletes performed significantly better in the body scheme tests, that is, fist width estimation (p = .024) and shoulder width estimation (p = .019), as well as in karate-specific kinesthesia tests, that is, single punch (p = .010) and triple punch (p = .001). This study confirms competitive karate athletes have significantly better somatognosis, and better accuracy when performing quick dynamic movements compared with the general population.

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Erik Lundkvist, Henrik Gustafsson, Daniel Madigan, Sören Hjälm, and Anton Kalén

The present study examined levels of emotional exhaustion, a key symptom of burnout, in Swedish professional and semiprofessional sport coaches in comparison to the normative values specified in the Maslach Burnout Inventory manual, and to the clinical cutoffs developed by Kleijweg, Verbraak, and Van Dijk. The sample contained 318 Swedish coaches (M age = 42.7 years, 12% female) working at least 50% full time away from both team (60%) and individual (40%) sports. Our study shows that, in general, coaches in this sample experience lower average levels of exhaustion than normative samples both regarding the Maslach Burnout Inventory and clinical cutoffs. Two groups of coaches did, however, stand out. Coaches living in single households as well as coaches working part time had higher risk of severe levels of emotional exhaustion. These results place coach exhaustion levels in relation to other occupations and highlight that in this sample, the coaching profession does not stand out as more emotionally exhausting than other occupations.

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Megan J. Schroeder, Samuel A. Acuña, Chandramouli Krishnan, and Yasin Y. Dhaher

Changes in knee mechanics following anterior cruciate ligament (ACL) reconstruction are known to be magnified during more difficult locomotor tasks, such as when descending stairs. However, it is unclear if increased task difficulty could distinguish differences in forces generated by the muscles surrounding the knee. This study examined how knee muscle forces differ between individuals with ACL reconstruction with different graft types (hamstring tendon and patellar tendon autograft) and “healthy” controls when performing tasks with increasing difficulty. Dynamic simulations were used to identify knee muscle forces in 15 participants when walking overground and descending stairs. The analysis was restricted to the stance phase (foot contact through toe-off), yielding 162 separate simulations of locomotion in increasing difficulty: overground walking, step-to-floor stair descent, and step-to-step stair descent. Results indicated that knee muscle forces were significantly reduced after ACL reconstruction, and stair descent tasks better discriminated changes in the quadriceps and gastrocnemii muscle forces in the reconstructed knees. Changes in quadriceps forces after a patellar tendon graft and changes in gastrocnemii forces after a hamstring tendon graft were only revealed during stair descent. These results emphasize the importance of incorporating sufficiently difficult tasks to detect residual deficits in muscle forces after ACL reconstruction.

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Katherine Holland, Justin A. Haegele, Xihe Zhu, and Jonna Bobzien

This study explored the experiences of students with orthopedic impairments in integrated physical education (PE) classes. An interpretative phenomenological analysis research approach was used, and six students with orthopedic impairments (age = 10–14 years) served as participants. Data sources were semistructured, audiotaped interviews and reflective interview notes. Based on data analysis, three themes were developed—“Without it, they probably would like, just treat me normal,” visibility, disclosure, and expectations; “I sit out,” limited participation and a lack of modifications/accommodations; and “PE doesn’t feel great,” social interactions and perception of self. The experiences portrayed throughout these themes highlight the marginalization and lack of access that the participants encountered in their integrated PE classes. The findings indicated that PE professionals working with students with orthopedic impairments may benefit from reflecting on personal biases and their instructional practices in an effort to improve the quality of PE experiences for these students.

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Jônatas Augusto Cursiol, Tarine Botta de Arruda, Fábio Yuzo Nakamura, and Ricardo Augusto Barbieri

The purpose of this study was to investigate the effects of three simulated goalball games on neuromuscular, physiological, perceptual, and technical parameters. Ten male players underwent assessments before and immediately after each game. Heart rate was recorded at rest and during all games that were entirely filmed for further technical performance analysis. Exercise significantly decreased knee extensor muscles peak force and percentage of voluntary activation after the second and third games, indicating the presence of central fatigue. Heart rate responses remained predominantly in a range equivalent to moderate activity intensity in all games. In addition, perceptual parameters were associated with reduced frequency of throws and density of actions. These findings suggest significant implications for the management of physical training, game strategy during a competition, and fixture change from three to two games per day.

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Mark L. Latash

This review of movement stability, optimality, and agility is based on the theory of motor control with changes in spatial referent coordinates for the effectors, the principle of abundance, and the uncontrolled manifold hypothesis. A new optimality principle is suggested based on the concept of optimal sharing corresponding to a vector in the space of elemental variables locally orthogonal to the uncontrolled manifold. Motion along this direction is associated with minimal components along the relatively unstable directions within the uncontrolled manifold leading to a minimal motor equivalent motion. For well-practiced actions, this task-specific criterion is followed in spaces of referent coordinates. Consequences of the suggested framework include trade-offs among stability, optimality, and agility, unintentional changes in performance, hand dominance, finger specialization, individual traits in performance, and movement disorders in neurological patients.

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Carolina Gutiérrez-Álvarez, Joshua Colomar, Ernest Baiget, Santos Villafaina, and Juan Pedro Fuentes-García

This study aimed to analyze the effect of a variable practice training in the double wall right forehand by using wrist weights. Thirty-four experienced padel players participated in this study. Players were randomly distributed in two groups (control group [CG] and training group [TG]). The TG performed 1 month of variable training, induced by weighted wrist bands, twice a week, with the same number of sessions and volume of training as the CG. TG obtained significant difference in posttest measurements (effect size = 0.437) in terms of the number of successful shots compared to CG (effect size = 0.027). These findings showed a significant effect of the TG with respect to the CG. Results reinforce the role of variability in the exploration and reinforcement of motor learning.

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Kazumichi Ae, Dave Burke, Takashi Kawamura, and Sekiya Koike

The objectives of this study were to (1) investigate the effect of the timing of the upper body joint motions in baseball batting on the bat-head speed and (2) develop and evaluate a simulation model inputting the individual hand forces on the bat. Twenty-three male collegiate baseball players performed tee batting set at waist height. A 10-segment angle-driven simulation model consisting of a bat and upper body was driven using the coordinate data of the standard motion. Performance optimization was conducted by changing the timing of the joint angle time histories of the upper body to increase the maximum bat-head speed. The optimization simultaneously estimated the individual hand forces by polynomial approximation dependent on the total bat forces to assess joint torques of the upper body. The bat-head speed increased to 39.2 m/s from 35.6 m/s, and the optimized timings were characterized by the earlier timing of the barrel-side elbow supination, wrist radial flexion, torso right lateral flexion, and the later timing of the barrel-side shoulder abduction. It is concluded that the skillful coordination of the individual joint movements for the upper body can produce a higher bat-head speed through effective sequencing of proximal to distal movements.

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Caleb D. Johnson, Jereme Outerleys, and Irene S. Davis

Several open-source platforms for markerless motion capture offer the ability to track 2-dimensional (2D) kinematics using simple digital video cameras. We sought to establish the performance of one of these platforms, DeepLabCut. Eighty-four runners who had sagittal plane videos recorded of their left lower leg were included in the study. Data from 50 participants were used to train a deep neural network for 2D pose estimation of the foot and tibia segments. The trained model was used to process novel videos from 34 participants for continuous 2D coordinate data. Overall network accuracy was assessed using the train/test errors. Foot and tibia angles were calculated for 7 strides using manual digitization and markerless methods. Agreement was assessed with mean absolute differences and intraclass correlation coefficients. Bland–Altman plots and paired t tests were used to assess systematic bias. The train/test errors for the trained network were 2.87/7.79 pixels, respectively (0.5/1.2 cm). Compared to manual digitization, the markerless method was found to systematically overestimate foot angles and underestimate tibial angles (P < .01, d = 0.06–0.26). However, excellent agreement was found between the segment calculation methods, with mean differences ≤1° and intraclass correlation coefficients ≥.90. Overall, these results demonstrate that open-source, markerless methods are a promising new tool for analyzing human motion.

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Danica Janicijevic and Amador Garcia-Ramos

This systematic review aimed to synthesize the current evidence on the feasibility of volitional reaction time (RT) tests to evaluate the information processing abilities of athletes. Four databases were searched, and, finally, 38 studies exploring the reliability, validity, or sensitivity of RT tests were included. Seven studies explored the reliability, which ranged from poor to excellent, while only three studies explored the validity of RT tests. The most important downside of the majority of the implemented RT tests is their nonspecific nature (i.e., stimulus and response did not resemble the sports actions). Sports scientists should focus on developing RT tests that are specific for each sport and refine the testing procedures to obtain accurate, reproducible, and sensitive measurements of RT.