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John Charles Bradbury

This study examines the determinants of Major League Soccer team attendance during the league’s recent era of growth. The estimates indicated that regular-season on-field performance is positively associated with attendance, but the returns to success are diminishing. The estimates identified positive novelty effects for newer teams and soccer-specific stadiums, but not for stadium age. Income and attendance were positively correlated, which indicates that Major League Soccer matches are a normal good. The population size, Hispanic share of the population, presence of other major-league franchises, and number of designated players on a team did not appear to be strong determinants of seasonal attendance.

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Pierre Lepage, Gordon A. Bloom and William R. Falcão

The purpose of this study was to understand the learning experiences and acquisition of knowledge of youth parasport coaches. Five able-bodied male participants (M = 39 years old), who coached youth with a physical disability for an average of 7.4 years, participated in individual interviews. An inductive thematic analysis identified patterns within and across the data, allowing for description and interpretation of the meaning and importance of the themes. The results showed that coaches learned mostly from informal experiences, particularly through mentoring, trial and error, or use of technology. In addition, these learning opportunities were influenced by personal, environmental, and social factors. These findings can help to guide current and future generations of coaches of youth participants with a physical disability by highlighting available resources and addressing several barriers and facilitators to their learning.

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Jeanette Gustat, Christopher E. Anderson and Sandy J. Slater

Background: Spaces that promote play are important for the physical, social, and psychological growth of children. Public spaces, including playgrounds, provide an important venue for children to engage in play. A simple tool is needed to evaluate playground features and conditions. Methods: A simple play space audit instrument to assess the presence and condition of playground features was tested on a sample of 70 playgrounds during the summer of 2017, in Chicago, IL. Duplicate observations were collected on 17 playgrounds. Frequencies of features were tabulated, and reliability of variables was assessed using percent agreement and kappa statistic. Scores were created to summarize playground “playability,” overall and within domains of general overview, surface, path, and play equipment/structure features. Results: The tool demonstrated acceptable reliability with high kappa values between .79 and .90 for all items in domains. The overall score, general overview score, and play equipment/structure scores were correlated with mean playground usage. Conclusions: This brief instrument allows reliable assessment of playground features and their conditions. The scoring method generates a summary of playground conditions and features, which facilitates comparison of playgrounds. This tool has the potential to assist communities in evaluating their play spaces and identifying where to focus resources for improvements.

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Juana Willumsen and Fiona Bull

Background: Physical inactivity is a leading risk factor for global mortality and a contributor to the increase in overweight and obesity. The Commission on Ending Childhood Obesity identified the need for guidance on physical activity, particularly for early childhood (<5 y), a period of rapid physical and cognitive development. Methods: The World Health Organization (WHO) has developed the first global guidelines on physical activity, sedentary, and sleep behaviors, building upon high-quality systematic reviews. The WHO guideline process is a rigorous, systematic, and transparent method for the development of recommendations, using the Grading of Recommendations Assessment, Development and Evaluation Evidence to Decision framework. It takes into consideration the strength of the evidence as well as values and preferences, benefits and harms, equity and human rights. Results: The authors summarize the first global guidelines on time spent in physical activity, sedentary behavior (including screen time and time spent restrained), and sleep patterns in infants (birth to 1 y of age), toddlers (1–2.9 y of age), and preschoolers (3–4.9 y of age). Conclusions: WHO is actively disseminating and supporting implementation of these guidelines by national adoption and adaptation, through links with early childhood development and the Global Action Plan on Physical Activity 2018–2030.

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Christopher A. DiCesare, Scott Bonnette, Gregory D. Myer and Adam W. Kiefer

Biomechanical analysis can effectively identify factors associated with task performance and injury risk, but often does not account for the interaction among the components that underlie task execution. Uncontrolled manifold (UCM) analyses were applied to data from 38 female, adolescent athletes performing single-leg drop landings and were used to differentiate successful and unsuccessful task performance by examining the frontal plane joint variance within the UCM (V UCM) that stabilized the horizontal center of mass position (V UCM) and within the orthogonal subspace (V ORT). The UCM revealed stronger coordination, indicated by the V UCM/V ORT ratio, in the successful condition. This may inform future research examining reduced motor coordination in failed movement tasks and its relation to injury risk and allow for targeted interventions that consider coordination processes rather than joint-specific outcomes.

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Samuel T. Tebeck, Jonathan D. Buckley, Clint R. Bellenger and Jamie Stanley

Purpose: To investigate the effect of a 5-day short-term heat acclimation (STHA) protocol in dry (43°C and 20% relative humidity) or humid (32°C and 80% relative humidity) environmental conditions on endurance cycling performance in temperate conditions (21°C). Methods: In a randomized, cross-over design, 11 cyclists completed each of the two 5-day blocks of STHA matched for heat index (44°C) and total exposure time (480 min), separated by 30 days. Pre- and post-STHA temperate endurance performance (4-min mean maximal power, lactate threshold 1 and 2) was assessed; in addition, a heat stress test was used to assess individual levels of heat adaptation. Results: Differences in endurance performance were unclear. Following dry STHA, gross mechanical efficiency was likely reduced (between-condition effect size dry vs humid −0.59; 90% confidence interval, −1.05 to −0.15), oxygen uptake was likely increased for a given workload (0.64 [0.14 to 1.07]), and energy expenditure likely increased (0.59 [0.17 to 1.03]). Plasma volume expansion at day 5 of acclimation was similar (within-condition outcome 4.6% [6.3%] and 5.3% [5.1%] dry and humid, respectively) but was retained for 3 to 4 days longer after the final humid STHA exposure (−0.2% [8.1%] and 4.5% [4.2%] dry and humid, respectively). Sweat rate was very likely increased during dry STHA (0.57 [0.25 to 0.89]) and possibly increased (0.18 [−0.15 to 0.50]) during humid STHA. Conclusion: STHA induced divergent adaptations between dry and humid conditions, but did not result in differences in temperate endurance performance.

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Cameron T. Gibbons, Polemnia G. Amazeen and Aaron D. Likens

Variability is commonly observed in complex behavior, such as the maintenance of upright posture. The current study examines the value added by using nonlinear measures of variability to identify dynamic stability instead of linear measures that reflect average fluctuations about a mean state. The largest Lyapunov exponent (λ1) and SD were calculated on mediolateral movement as participants performed a sit-to-stand task on a stable and unstable platform. Both measures identified changes in movement across postures, but results diverged when participants stood on the unstable platform. Large SD indicated an increase in movement variability, but small λ1 identified those movements as stable and controlled. The results suggest that a combination of linear and nonlinear analyses is useful in identifying the proportion of observed variability that may be attributed to structured, controlled sources. Nonlinear measures of variability, like λ1, can further be used to make predictions about transitions between stable postures and to identify a system’s resistance to disruption from external perturbations. Those features make nonlinear analyses highly applicable to both human movement research and clinical practice.

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Stephanie A. Hooker, Laura B. Oswald, Kathryn J. Reid and Kelly G. Baron

Background: Little is known about how daily fluctuations in health behaviors relate to chronic disease risk. The goal of this study was to examine whether variability in physical activity, caloric intake, and sleep is related to body composition (body mass index and body fat percentage). Methods: Healthy adults (N = 103; 64% female) were monitored for 7 days to assess physical activity (SenseWear Armband), caloric intake (daily food diaries), and sleep duration and timing (Actiwatch Spectrum). Data were analyzed using correlations (between- and within-subjects correlations) and regression. Results: The results demonstrated that variabilities in physical activity, caloric intake, and sleep were unrelated. Caloric intake and sleep variability were unrelated to body composition. At greater levels of physical activity variability, any level of physical activity was protective for body composition. Conclusions: These results suggest that among healthy adults, variabilities in health behaviors may be independent of each other, and physical activity variability may be more strongly related to body composition among those who are less active.

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Cui Zhang, Qipeng Song, Wei Sun and Yu Liu

Daily stair activities have become increasingly challenging for older adults with deterioration in physical and cognitive capabilities. However, the dynamic stability of older adults during stair descent under a concurrent dual-task condition remains undetermined. The gait and dynamic stability variables of 40 healthy older adults were measured under single- and dual-task conditions during stair descent. The step length, step width, and single support time did not significantly increase (p > .05) under the dual-task condition during stair descent. The medial–lateral center of mass velocity significantly increased (p < .003), whereas the medial–lateral margin of dynamic stability value significantly decreased (p < .006) at the landing and initial single support under the dual-task condition during stair descent. The self-regulatory ability of healthy older adults under the dual-task condition during stair descent was underestimated. Dual tasking displayed a positive impact on the anterior–posterior dynamic stability of healthy older adults.

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Mostafa Zarei, Hamed Abbasi, Abdolhamid Daneshjoo, Mehdi Gheitasi, Kamran Johari, Oliver Faude, Nikki Rommers and Roland Rössler

Purpose: The “11+ Kids” injury-prevention program has been shown to reduce injuries and related costs in youth football players less than 14 y of age. A major argument to convince coaches to use this exercise-based injury-prevention program is a potential performance enhancement of the players. Therefore, this study investigated the effects of the “11+ Kids” program on isokinetic strength. Methods: Two teams were randomly assigned to the intervention and control groups. The intervention group replaced their warm-up by the “11+ Kids” and the control group warmed up as usual. Two days before and after the 10-wk intervention, isokinetic strength of the hip adductors and abductors, knee flexors and extensors, and ankle invertors and evertors was tested. Results: Thirty-one players (mean age 11.5 [0.8] y) completed the study. The intervention group showed large improvements in all isokinetic strength measures (P < .001 for all measures; Cohen d = 0.8–1.4), whereas the control group only showed negligible to medium positive effects (P values ranging from .006 to .718; Cohen d = −0.1 to 0.7). The intervention was beneficial compared with the control group regarding isokinetic strength of the hip adductors (P < .001), knee flexors (P = .002), and ankle evertors (P < .001) and invertors (P = .005). Conclusions: Given the relatively short intervention period of 10 wk, the observed improvements relate to a practically meaningful effect of the intervention. The gain in strength may improve players’ performance and may contribute to a reduction of injury risk in the long-term application.