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Dale R. Wagner and James D. Cotter

Ultrasound is an appealing tool to assess body composition, combining the portability of a field method with the accuracy of a laboratory method. However, unlike other body composition methods, the effect of hydration status on validity is unknown. This study evaluated the impact of acute hydration changes on ultrasound measurements of subcutaneous fat thickness and estimates of body fat percentage. In a crossover design, 11 adults (27.1 ± 10.5 years) completed dehydration and hyperhydration trials to alter body mass by approximately ±2%. Dehydration was achieved via humid heat (40 °C, 60% relative humidity) with exercise, whereas hyperhydration was via ingestion of lightly salted water. Ultrasound measurements were taken at 11 body sites before and after each treatment. Participants lost 1.56 ± 0.58 kg (−2.0 ± 0.6%) during the dehydration trial and gained 0.90 ± 0.21 kg (1.2 ± 0.2%) during the hyperhydration trial even after urination. The sum of fat thicknesses as measured by ultrasound differed by <0.90 mm across trials (p = .588), and ultrasound estimates of body fat percentage differed by <0.5% body fat. Ultrasound measures of subcutaneous adipose tissue were unaffected by acute changes in hydration status by extents beyond which are rare and overtly self-correcting, suggesting that this method provides reliable and robust body composition results even when subjects are not euhydrated.

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Manuel J. Escalona, Daniel Bourbonnais, Michel Goyette, Damien Le Flem, Cyril Duclos, and Dany H. Gagnon

The effects of walking speeds on lower-extremity muscle synergies (MSs) were investigated among 20 adults who walked 20 m at SLOW (0.6 ± 0.2 m/s), natural (NAT; 1.4 ± 0.1 m/s), and FAST (1.9 ± 0.1 m/s) speeds. Surface electromyography of eight lower-extremity muscles was recorded before extracting MSs using a nonnegative matrix factorization algorithm. Increasing walking speed tended to merge MSs associated with weight acceptance and limb deceleration, whereas reducing walking speed does not change the number and composition of MSs. Varying gait speed, particularly decreasing speed, may represent a gait training strategy needing additional attention given its effects on MSs.

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Marco Beato, Sergio Maroto-Izquierdo, Anthony N. Turner, and Chris Bishop

Due to the negative effects that injuries have on performance, club finances, and long-term player health (permanent disability after a severe injury), prevention strategies are an essential part of both sports medicine and performance. Purpose: To summarize the current evidence regarding strength training for injury prevention in soccer and to inform its evidence-based implementation in research and applied settings. Conclusions: The contemporary literature suggests that strength training, proposed as traditional resistance, eccentric, and flywheel training, may be a valid method to reduce injury risk in soccer players. Training strategies involving multiple components (eg, a combination of strength, balance, plyometrics) that include strength exercises are effective at reducing noncontact injuries in female soccer players. In addition, the body of research currently published supports the use of eccentric training in sports, which offers unique physiological responses compared with other resistance exercise modalities. It seems that the Nordic hamstring exercise, in particular, is a viable option for the reduction of hamstring injuries in soccer players. Moreover, flywheel training has specific training peculiarities and advantages that are related to the combination of both concentric and eccentric contraction, which may play an important role in injury prevention. It is the authors’ opinion that strength and conditioning coaches should integrate the strength training methods proposed here in their weekly training routine to reduce the likelihood of injuries in their players; however, further research is needed to verify the advantages and disadvantages of these training methods to injury prevention using specific cohorts of soccer players.

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Catherine E. Draper, Karen Milton, and Jasper Schipperijn

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Daniella M. DiGuglielmo, Mireille E. Kelley, Mark A. Espeland, Zachary A. Gregory, Tanner D. Payne, Derek A. Jones, Tanner M. Filben, Alexander K. Powers, Joel D. Stitzel, and Jillian E. Urban

To reduce head impact exposure (HIE) in youth football, further understanding of the context in which head impacts occur and the associated biomechanics is needed. The objective of this study was to evaluate the effect of contact characteristics on HIE during player versus player contact scenarios in youth football. Head impact data and time-synchronized video were collected from 4 youth football games over 2 seasons in which opposing teams were instrumented with the Head Impact Telemetry (HIT) System. Coded contact characteristics included the player’s role in the contact, player speed and body position, contact height, type, and direction, and head contact surface. Head accelerations were compared among the contact characteristics using mixed-effects models. Among 72 instrumented athletes, 446 contact scenarios (n = 557 impacts) with visible opposing instrumented players were identified. When at least one player had a recorded impact, players who were struck tended to have higher rotational acceleration than players in striking positions. When both players had a recorded impact, lighter players and taller players experienced higher mean head accelerations compared with heavier players and shorter players. Understanding the factors influencing HIE during contact events in football may help inform methods to reduce head injury risk.

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Philip J. Morgan, Clare E. Collins, Alyce T. Barnes, Emma R. Pollock, Stevie-Lee Kennedy, Ryan J. Drew, Kristen L. Saunders, Jacqueline A. Grounds, Anna T. Rayward, and Myles D. Young

Background: Few lifestyle programs for young children have targeted fathers. This study examined the feasibility of a lifestyle intervention for fathers and their preschool-aged children. Method: A total of 24 father/preschool child dyads were recruited from Newcastle, Australia, into a single-arm, feasibility trial (baseline and 3-mo postbaseline assessments). The 9-session program aimed to improve physical activity and dietary habits of fathers and children. A priori feasibility benchmarks targeted recruitment (15 dyads), eligibility rate (>60%), attendance (80%), retention (≥85%), and program acceptability (≥4 out of 5). Acceptability of data collection procedures, research team program/resource management, home-program compliance, and preliminary intervention outcomes were also assessed. Results: Feasibility benchmarks were surpassed for recruitment (24 dyads), eligibility rate (61.5%), attendance (89%), retention (100%), and program acceptability (4.6 out of 5). Data collection procedures were acceptable. Challenges included mothers reporting their own dietary intake rather than their child’s, children moving during body composition measurement, and resetting pedometers. Resource and program management were excellent. Most families met home-program requirements (83%). Preliminary intervention outcomes were encouraging for fathers and children. Conclusion: Program feasibility was demonstrated by excellent recruitment, attendance, acceptability, retention, program administration, and promising preliminary intervention outcomes. A few data collection difficulties were identified. A larger scale efficacy trial is warranted.

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Meena Makhija, Jasobanta Sethi, Chitra Kataria, Harpreet Singh, Paula M. Ludewig, and Vandana Phadke

Two-dimensional fluoroscopic imaging allows measurement of small magnitude humeral head translations that are prone to errors due to optical distortion, out-of-plane imaging, repeated manual identification of landmarks, and magnification. This article presents results from in vivo and in vitro fluoroscopy-based experiments that measure the errors and variability in estimating the humeral head translated position in true scapular plane and axillary views. The errors were expressed as bias and accuracy. The variability with repeated digitization was calculated using the intraclass correlation coefficient (ICC) and the standard error of measurement. Optical distortion caused underestimation of linear distances. The accuracy was 0.11 and 0.43 mm for in vitro and in vivo experiments, respectively, for optical distortion. The intrarater reliability was excellent for both views (ICC = .94 and .93), and interrater reliability was excellent (ICC = .95) for true scapular view but moderate (ICC = .74) for axillary views. The standard error of measurement ranged from 0.27 to 0.58 mm. The accuracy for the humeral head position in 10° out of true scapular plane images ranged from 0.80 to 0.87 mm. The current study quantifies the magnitude of error. The results suggest that suitable measures could be incorporated to minimize errors and variability for the measurement of glenohumeral parameters.

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Joanna Horne, Nichola Kentzer, Lee Smith, Mike Trott, and Jitka Vseteckova

Background: It is estimated that 17% of the UK adult population are informal carers, usually for a family member, with a majority reporting that they are not able to engage in physical activity as much as they would like. The aim of this review is to provide a greater understanding of the prevalence of, and barriers and facilitators to, physical activity of informal carers in the United Kingdom. Methods: A systematic review of relevant databases and grey literature was undertaken, following Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidance, from its inception until July 17, 2020. Results: Barriers to physical activity include increasing aging, not wanting to leave the caree alone, the caree being unable to take part in activities, health conditions, fatigue, lack of time, and difficulties in changing the routine for the caree. Facilitators include an appreciation of the benefits of engaging in exercise, previous participation in activities, group activities with similar people, and having some free time. Conclusions: Due to the paucity of research into the prevalence of, and barriers and facilitators to, physical activity in informal carers in the United Kingdom, this systematic review highlights the need for further research, focusing primarily on the physical activity of informal carers caring for individuals with a range of conditions. A further systematic review exploring these issues internationally is warranted.

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Katherine A.J. Daniels, Eleanor Drake, Enda King, and Siobhán Strike

Cutting maneuvers can be executed at a range of angles and speeds, and these whole-body task descriptors are closely associated with lower-limb mechanical loading. Asymmetries in angle and speed when changing direction off the operated and nonoperated limbs after anterior cruciate ligament reconstruction may therefore influence the interpretation of interlimb differences in joint-level biomechanical parameters. The authors hypothesized that athletes would reduce center-of-mass heading angle deflection and body rotation during the change-of-direction stance phase when cutting from the operated limb, and would compensate for this by orienting their center-of-mass trajectory more toward the new intended direction of travel prior to touchdown. A total of 144 male athletes 8 to 10 months after anterior cruciate ligament reconstruction performed a maximum-effort sidestep cutting maneuver while kinematic, kinetic, and ground reaction force data were recorded. Peak ground reaction force and knee joint moments were lower when cutting from the operated limb. Center-of-mass heading angle deflection during stance phase was reduced for cuts performed from the operated limb and was negatively correlated with heading angle at touchdown. Between-limb differences in body orientation and horizontal velocity at touchdown were also observed. These systematic asymmetries in cut execution may require consideration when interpreting joint-level interlimb asymmetries after anterior cruciate ligament reconstruction and are suggestive of the use of anticipatory control to co-optimize task achievement and mechanical loading.

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Jose A. Rodríguez-Marroyo, Beltrán González, Carl Foster, Ana Belén Carballo-Leyenda, and José G. Villa

Purpose: This study investigated the effect of cooldown modality (active vs passive) and duration (5, 10, and 15 min) on session rating of perceived exertion (sRPE). Secondarily, the possible influence of training sessions’ demand on this effect was studied. Methods: A total of 16 youth male soccer players (15.7 [0.4] y) completed 2 standardized training sessions per week across 6 weeks. During weeks 1 to 2, 3 to 4, and 5 to 6, cooldown lengths of 15, 10, and 5 minutes were studied, respectively. Using a crossover design, players were randomly assigned to 2 groups and each group performed 1 of 2 different cooldown interventions. Passive and active cooldown interventions based on static stretching and running exercises were studied. Heart rate and sRPE were recorded during all training sessions. Results: The lowest sRPE was observed when passive cooldown was performed. When the hardest training sessions were considered, a significant main effect of cooldown modality (P < .01) and duration (P < .05) and an interaction effect between these variables (P < .05) on sRPE were obtained. The lowest (P < .01) sRPE was observed during the longest cooldown (15 min). Conclusion: The findings suggest that sRPE may be sensitive to the selected cooldown modality and duration, especially following the most demanding training sessions.