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Peter M. Fowler, Wade Knez, Heidi R. Thornton, Charli Sargent, Amy E. Mendham, Stephen Crowcroft, Joanna Miller, Shona Halson and Rob Duffield

Purpose: To assess the efficacy of a combined light exposure and sleep hygiene intervention to improve team-sport performance following eastward long-haul transmeridian travel. Methods: Twenty physically trained males underwent testing at 09:00 and 17:00 hours local time on 4 consecutive days at home (baseline) and the first 4 days following 21 hours of air travel east across 8 time zones. In a randomized, matched-pairs design, participants traveled with (INT; n = 10) or without (CON; n = 10) a light exposure and sleep hygiene intervention. Performance was assessed via countermovement jump, 20-m sprint, T test, and Yo-Yo Intermittent Recovery Level 1 tests, together with perceptual measures of jet lag, fatigue, mood, and motivation. Sleep was measured using wrist activity monitors in conjunction with self-report diaries. Results: Magnitude-based inference and standardized effect-size analysis indicated there was a very likely improvement in the mean change in countermovement jump peak power (effect size 1.10, ±0.55), and likely improvement in 5-m (0.54, ±0.67) and 20-m (0.74, ±0.71) sprint time in INT compared with CON across the 4 days posttravel. Sleep duration was most likely greater in INT both during travel (1.61, ±0.82) and across the 4 nights following travel (1.28, ±0.58) compared with CON. Finally, perceived mood and motivation were likely worse (0.73, ±0.88 and 0.63, ±0.87) across the 4 days posttravel in CON compared with INT. Conclusions: Combined light exposure and sleep hygiene improved speed and power but not intermittent-sprint performance up to 96 hours following long-haul transmeridian travel. The reduction of sleep disruption during and following travel is a likely contributor to improved performance.

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Corey A. Pew, Sarah A. Roelker, Glenn K. Klute and Richard R. Neptune

The coupling between the residual limb and the lower-limb prosthesis is not rigid. As a result, external loading produces movement between the prosthesis and residual limb that can lead to undesirable soft-tissue shear stresses. As these stresses are difficult to measure, limb loading is commonly used as a surrogate. However, the relationship between limb loading and the displacements responsible for those stresses remains unknown. To better understand the limb motion within the socket, an inverse kinematic analysis was performed to estimate the motion between the socket and tibia for 10 individuals with a transtibial amputation performing walking and turning activities at 3 different speeds. The authors estimated the rotational stiffness of the limb-socket body to quantify the limb properties when coupled with the socket and highlight how this approach could help inform prosthetic prescriptions. Results showed that peak transverse displacement had a significant, linear relationship with peak transverse loading. Stiffness of the limb-socket body varied significantly between individuals, activities (walking and turning), and speeds. These results suggest that transverse limb loading can serve as a surrogate for residual-limb shear stress and that the setup of a prosthesis could be individually tailored using standard motion capture and inverse kinematic analyses.

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Brian T. Tomblin, N. Stewart Pritchard, Tanner M. Filben, Logan E. Miller, Christopher M. Miles, Jillian E. Urban and Joel D. Stitzel

The objective of this research was to characterize head impacts with a validated mouthpiece sensor in competitive youth female soccer players during a single season with a validated mouthpiece sensor. Participants included 14 youth female soccer athletes across 2 club-level teams at different age levels (team 1, ages 12–13 y; team 2, ages 14–15 y). Head impact and time-synchronized video data were collected for 66 practices and games. Video data were reviewed to characterize the type and frequency of contact experienced by each athlete. A total of 2216 contact scenarios were observed; heading the ball (n = 681, 30.7%) was most common. Other observed contact scenarios included collisions, dives, falls, and unintentional ball contact. Team 1 experienced a higher rate of headers per player per hour of play than team 2, while team 2 experienced a higher rate of collisions and dives. A total of 935 video-verified contact scenarios were concurrent with recorded head kinematics. While headers resulted in a maximum linear acceleration of 56.1g, the less frequent head-to-head collisions (n = 6) resulted in a maximum of 113.5g. The results of this study improve the understanding of head impact exposure in youth female soccer players and inform head impact exposure reduction in youth soccer.

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Jessica L. Unick, Michael P. Walkup, Michael E. Miller, John W. Apolzan, Peter H. Brubaker, Mace Coday, James O. Hill, John M. Jakicic, Roeland J.W. Middelbeek, Delia West, Rena R. Wing and the Look AHEAD Research Group

Background: To examine the relationship between early physical activity (PA) adoption (2, 3, and 4 mo) and longer-term PA adherence (1 y) among individuals who were inactive at baseline and received a lifestyle intervention. Methods: Participants (n = 637) received weekly behavioral weight loss sessions, calorie reduction, and PA goals (50–175 min/wk progression). PA was assessed via self-reported measures at baseline, months 2 to 4, and 1 year. Results: PA at months 2 to 4 was significantly correlated with PA at 1 year (rs = .29–.35, P < .01). At all early time points, those failing to meet the prescribed PA goal (early nonadopters) engaged in significantly less PA at 1 year than those meeting the early PA goal (initial adopters). For example, using 2-month criteria, initial adopters engaged in 108.3 minutes per week more at 1 year compared with early nonadopters (P < .01) and had 2.8 times the odds (95% confidence interval, 1.9–4.2) of meeting the 1-year PA goal (≥175 min/wk, P < .01). Conclusions: Failure to achieve PA goals at 2, 3, or 4 months results in less overall PA at 1 year. Thus, PA observed as early as month 2 may be a useful indicator for identifying at-risk individuals who may benefit from more intensive PA intervention strategies.

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Eduardo L. Caputo and Felipe F. Reichert

Background: This scoping review aimed to identify the available evidence related to physical activity (PA) and the coronavirus disease (COVID-19) pandemic. Methods: A search in 6 databases (PubMed, Embase, SPORTDiscus, Scopus, Web of Science, and CINAHL) was conducted on July 23, 2020. Medical subject headings and keywords related to PA and COVID-19 were combined to conduct the online search, which covered the period from January to July 2020. Results: Overall, 1784 articles were retrieved. After duplicate removal and title, abstract, and full-text screening, 41 articles were included. Most of the included studies were quantitative and collected data through online interviews/questionnaires, with sample sizes larger than 100 and composed by adults and older adults. Changes in PA levels due to the COVID-19 pandemic were the most assessed outcome, followed by the association between mental health issues and PA. Only 2 studies assessed the direct effects of PA on COVID-19. Conclusion: Most of the evidence identified a decrease in PA levels due to social distancing measures and that PA might help to decrease the mental health burden related to the COVID-19 outbreak.

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Dechristian França Barbieri, Luiz Augusto Brusaca, Svend Erik Mathiassen and Ana Beatriz Oliveira

Background: Sit–stand desks have been suggested as an initiative to increase posture variation among office workers. However, there is limited evidence of what would be preferable combinations of time sitting and standing. The aim of this study was to determine and compare perceived pleasantness, acceptability, pain, and fatigue for 5 time patterns of sitting and standing at a sit–stand desk. Methods: Thirty postgraduate students were equally divided into a normal-weight (mean body mass index 22.8 kg/m2) and an overweight/obese (mean body mass index 28.1 kg/m2) group. They performed 3 hours of computer work at a sit–stand desk on 5 different days, each day with a different time pattern (A: 60-min sit/0-min stand; B: 50/10; C: 40/20; D: 30/30; E: 20/40). Pleasantness, acceptability, pain, and fatigue ratings were obtained at the beginning and at the end of the 3-hour period. Results: High ratings of pleasantness were observed for time patterns B, C, and D in both groups. All participants rated acceptability to be good for time patterns A to D. A minor increase in perceived fatigue and pain was observed in time pattern E. Conclusion: For new sit–stand desk users, regardless of body mass index, 10 to 30 minutes of standing per hour appears to be an amenable time pattern.