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Yumeng Li, Shuqi Zhang and Christina Odeh

The purposes of the study were (1) to compare postural sway between participants with Parkinson’s disease (PD) and healthy controls and (2) to develop and validate an automated classification of PD postural control patterns using a machine learning approach. A total of 9 participants in the early stage of PD and 12 healthy controls were recruited. Participants were instructed to stand on a force plate and maintain stillness for 2 minutes with eyes open and eyes closed. The center of pressure data were collected at 50 Hz. Linear displacements, standard deviations, total distances, sway areas, and multiscale entropy of center of pressure were calculated and compared using mixed-model analysis of variance. Five supervised machine learning algorithms (ie, logistic regression, K-nearest neighbors, Naïve Bayes, decision trees, and random forest) were used to classify PD postural control patterns. Participants with PD exhibited greater center of pressure sway and variability compared with controls. The K-nearest neighbor method exhibited the best prediction performance with an accuracy rate of up to 0.86. In conclusion, participants with PD exhibited impaired postural stability and their postural sway features could be identified by machine learning algorithms.

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Seth T. Strayer, Seyed Reza M. Moghaddam, Beth Gusenoff, Jeffrey Gusenoff and Kurt E. Beschorner

Pressure offloading is critical to diabetic foot ulcer healing and prevention. A novel product has been proposed to achieve this offloading with an insole that can be easily modified for each user. This insole consists of pressurized bubbles that can be selectively perforated and depressurized to redistribute weight to the nonulcer region of the foot. However, the effect of the insole design parameters, for example, bubble height and stiffness, on offloading effectiveness is unknown. To this end, a 3-dimensional finite element model was developed to simulate contact between the rearfoot and insole. The geometry of the calcaneus bone and soft tissue was based on the medical images of an average male patient, and material properties and loading conditions based on the values reported in the literature were used. The model predicts that increasing bubble height and stiffness leads to a more effectively offloaded region. However, the model also predicts that increasing stiffness leads to increasing contact pressures on the surrounding soft tissue. Thus, a combination of insole design parameters was determined, which completely offloads the desired region, while simultaneously reducing the contact pressure on the surrounding soft tissue. This design is expected to aid in diabetic foot ulcer healing and prevention.

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Jason M. Avedesian, Tracey Covassin and Janet S. Dufek

Recent evidence suggests previously concussed athletes are at greater risk for lower-extremity (LE) injuries than are controls. However, little is known regarding the influence of sports-related concussion (SRC) on landing biomechanics that may provide a mechanistic rationale for LE injury risk. The purpose of this investigation was to examine LE drop-landing biomechanics in adolescent athletes with and without a previous SRC history. Participants included 10 adolescent athletes with an SRC history and 11 controls from multiple sports. Three-dimensional kinematic and kinetic data associated with LE injury risk were analyzed across 5 trials for 30- and 60-cm landing heights. Multivariate analyses indicated group differences in landing patterns from the 30- (P = .041) and 60-cm (P = .015) landing heights. Follow-up analyses indicated that concussed adolescent athletes demonstrated significantly less ankle dorsiflexion and knee flexion versus controls when performing drop landings. Our findings suggest that previously concussed adolescent athletes complete drop-landing maneuvers with ankle and knee joint kinematic patterns that suggest greater risk for LE injury. While limitations such as sport variety and explicit LE injury history are present, the results of this study provide a possible biomechanical rationale for the association between SRC and LE injury risk.

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Pedro Ángel Latorre-Román, Juan Francisco Fernández-Povedano, Jesús Salas-Sánchez, Felipe García-Pinillos and Juan Antonio Párraga-Montilla

This study aimed to evaluate spatial and temporal perception in endurance runners as a mechanism of pacing control in comparison with other athletes (soccer players). A group of 38 endurance runners and 32 soccer players participated in this study. Runners displayed lower time differences and lower error than soccer players. Taking the athletic levels of endurance runners into consideration, significant differences (p = .011, Cohen’s d = 1.042) were found in the time differences (higher level group = 33.43 ± 29.43 vs. lower level group = 123.53 ±102.61). Significant correlations were found between time differences and performance in a Cooper test (r = −.546) and with the best time in a half marathon (r = .597). Temporal and spatial perception can be considered as a cognitive skill of endurance runners.

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Erika D. Van Dyke, Aaron Metzger and Sam J. Zizzi

Little research has integrated mindfulness and perfectionism, particularly within sports wherein athletes are judged on performance to a standard of perfection. The current study had two primary aims: (a) to explore profiles of mindfulness and perfectionism among intercollegiate gymnasts through a person-centered approach and (b) to analyze differences in objective performance across the resulting profiles. The analytic sample consisted of 244 NCAA gymnasts who completed self-report measures of mindfulness and perfectionism. Competitive performance records (i.e., national qualifying scores) were then gathered for participating gymnasts. Cluster analyses revealed a three-cluster solution; however, significant performance differences were not observed across the three profiles due to lower than desired power. Small to moderate effect size estimates provided some evidence that perfectionism may be adaptive to gymnastics performance. Elite-level athletes were represented across three distinct profiles, suggesting that more than one profile of characteristics may be adaptive for reaching high levels of performance.

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Anderson Nascimento Guimarães, Herbert Ugrinowitsch, Juliana Bayeux Dascal and Victor Hugo Alves Okazaki

To test Bernstein’s degrees of freedom (DF) hypothesis, the authors analyzed the effect of practice on the DF control and interjoint coordination of a Taekwondo kick. Thirteen inexperienced and 11 expert Taekwondo practitioners were evaluated. Contrary to Bernstein’s hypothesis, the inexperienced group froze the DF at the end of learning, reducing the joint range of motion of the knee. Moderate and strong cross-correlations between joints did not change, demonstrating that the interjoint coordination was maintained. The inexperienced group’s movement pattern was similar to that of the group of experts, from the beginning of the learning process. Thus, even after years of practice, experts continue to explore the strategy of freezing DF. The DF freeing/freezing sequence strategy was explored during the learning process, suggesting that DF-freezing/freeing strategies are task dependent.

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Jessica G. Hunter, Alexander M.B. Smith, Lena M. Sciarratta, Stephen Suydam, Jae Kun Shim and Ross H. Miller

Studies of running mechanics often use a standardized lab shoe, ostensibly to reduce variance between subjects; however, this may induce unnatural running mechanics. The purpose of this study was to compare the step rate, vertical average loading rate, and ground contact time when running in standardized lab shoes versus participants’ normal running shoes. Ground reaction forces were measured while the participants ran overground in both shoe conditions at a self-selected speed. The Student’s t-test revealed that the vertical average loading rate magnitude was smaller in lab shoes versus normal shoes (42.09 [11.08] vs 47.35 [10.81] body weight/s, P = .013), while the step rate (170.92 [9.43] vs 168.98 [9.63] steps/min, P = .053) and ground contact time were similar (253 [25] vs 251 [20] ms, P = .5227) and the variance of all outcomes was similar in lab shoes versus normal shoes. Our results indicate that using standardized lab shoes during testing may underestimate the loads runners actually experience during their typical mileage.

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Graig M. Chow, Matthew D. Bird, Nicole T. Gabana, Brandon T. Cooper and Martin A. Swanbrow Becker

Student-athletes are susceptible to mental health problems that disrupt optimal functioning and well-being. Despite having many protective factors, student-athletes represent an at-risk subgroup of college students who experience mental health concerns due to the distress of balancing multiple obligations. However, many student-athletes underutilize psychological services. Stigma is the main barrier preventing student-athletes from seeking help, and mental health literacy (MHL) interventions addressing knowledge and beliefs about mental disorders have traditionally been used to destigmatize mental illness. This study investigated the impact of a 4-week program on stigma, MHL, and attitudes and intentions toward seeking help with 33 National Collegiate Athletic Association Division I student-athletes. The program was composed of four science-based interventions—MHL, empathy, counter stereotyping, and contact—delivered face-to-face within a group setting. MHL, attitudes toward seeking help, and intentions to seek counseling improved from preintervention to postintervention and to 1-month follow-up. Self-stigma was reduced from preintervention to postintervention.

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Stijn Schouppe, Jessica Van Oosterwijck, Jan R. Wiersema, Stefaan Van Damme, Tine Willems and Lieven Danneels

The contribution of central factors to movement preparation (e.g., the contingent negative variation [CNV]) and the influence of fatigue on such factors are still unclear, even though executive cognitive functions are regarded as key elements in motor control. Therefore, this study examined CNV amplitude with electroencephalography in 22 healthy humans during a rapid arm movement task prior to and following three experimental conditions: (a) a no exertion/control condition, (b) a physical exertion, and (c) a cognitive exertion. CNV amplitude was affected neither by a single bout of physical/cognitive exertion nor by the control condition. Furthermore, no time-on-task effects of the rapid arm movement task on the CNV were found. Exertion did not affect cortical movement preparation, which is in contrast to previous findings regarding time-on-task effects of exertion on CNV. Based on the current findings, the rapid arm movement task is deemed suitable to measure cortical movement preparation, without being affected by learning effects and physical/cognitive exertion.

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Lydia M. Kocher, Jonisha P. Pollard, Ashley E. Whitson and Mahiyar F. Nasarwanji

Footwear plays an important role in worker safety. Work boots with safety toes are often utilized at mine sites to protect workers from hazards. Increasingly, mining operations require metatarsal guards in addition to safety toe protection in boots. While these guards provide additional protection, the impact of metatarsal guards on gait are unknown. This study aimed to measure the effects of 4 safety work boots, steel toe, and steel toe with metatarsal protection in wader- and hiker-style boots, on level and inclined walking gait characteristics, during ascent and descent. A total of 10 participants completed this study. A motion capture system measured kinematics that allowed for the calculation of key gait parameters. Results indicated that gait parameters changed due to incline, similar to previous literature. Wader-style work boots reduced ankle range of motion when ascending an incline. Hip, knee, and ankle ranges of motion were also reduced during descent for this style of boot. Wader-style boots with metatarsal guards led to the smallest ankle range of motion when descending an inclined walkway. From these results, it is likely that boot style affects gait parameters and may impact a miner’s risk for slips, trips, or falls.