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David J. Scott, Phil Marshall, Samuel T. Orange, and Massimiliano Ditroilo

Purpose: To compare the effects of variable-resistance complex training (VRCT) versus traditional complex training (TCT) on muscle architecture in rugby league players during a 6-week mesocycle. Methods: Twenty-four rugby league players competing in the British University & Colleges Sport (BUCS) Premier North Division were randomized to VRCT (n = 8), TCT (n = 8), or control (n = 8). Experimental groups completed a 6-week lower-body complex training intervention (2×/wk), which involved alternating high-load resistance exercise with plyometric exercise in the same session. The VRCT group performed resistance exercises at 70% of 1-repetition maximum (1RM) + 0% to 23% of 1RM from band resistance with a 90-second intracontrast rest interval, whereas the TCT group performed resistance exercise at 93% of 1RM with a 4-minute intracontrast rest interval. Muscle thickness (MT), pennation angle, and fascicle length (L f) were assessed for the vastus lateralis (VL) and gastrocnemius medialis using ultrasound imaging. Results: Both TCT and VRCT groups significantly improved VL MT and VL L f compared with control (all P < .05). Standardized within-group changes in MT and L f (Cohen d av  ± 95% CI) were moderate for TCT (d av  = 0.91 ± 1.0; d av  = 1.1 ± 1.1) and unclear for VRCT (d av  = 0.44 ± 0.99; d av  = 0.47 ± 0.99), respectively. Differences in change scores between TCT and VRCT were unclear. Conclusions: VRCT and TCT can be utilized during the competitive season to induce favorable MT and L f muscle architecture adaptations for the VL. TCT may induce greater muscle architecture adaptations of the VL, whereas VRCT may be of more practical value given the shorter intracontrast rest interval between resistance and plyometric exercises.

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Shaun Abbott, Wei En Leong, Tom Gwinn, Giovanni Luca Postiglione, James Salter, and Stephen Cobley

Purpose: To examine the longitudinal relationships between shoulder internal and external rotation (IR and ER) strength, maturity status, and swim performance (aim 1). To determine whether maturity status mediated (partially/fully) the relationship between shoulder IR/ER strength and performance in age-group swimmers (aim 2). Methods: Using a repeated-measures design, anthropometrics, maturity status, shoulder IR/ER strength, and 200-m front-crawl velocity were assessed over 3 competition seasons in N = 82 Australian male competitive swimmers (10–15 y). For aim 1, linear mixed models examined longitudinal relationships between assessed variables. For aim 2, causal mediation analyses examined proportional (in)direct contributions of maturity status between shoulder IR strength and swim performance. Results: For aim 1, linear mixed models identified a significant relationship between shoulder IR strength and swim performance over time (F 1,341.25 = 16.66, P < .001, marginal R 2 = .13, conditional R 2 = .91). However, maturity status was influential (ΔAkaike information criterion = −75.8, χ 2 = 19.98, P < .001), suggesting removal of the shoulder IR strength–swim velocity relationship (F 1,214.1 = 0.02, P = .88). For aim 2, mediation analyses identified maturity status as fully mediating the shoulder IR strength–swim velocity relationship (92.30%, P < .001). Conclusions: Shoulder IR and ER strength did not account for variance in longitudinal age-group swim performance independent of maturity status. Interindividual differences in maturity status fully explained the relationship between shoulder IR/ER strength and swim performance. For practitioners, findings promote the need to account for maturation status and question the rationale for upper-limb strength assessment during maturational years.

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Marco Panascì, Vittoria Ferrando, Ambra Bisio, Luca Filipas, Piero Ruggeri, and Emanuela Faelli

Purpose: To compare the effects of 2 small-sided games (SSGs), shuttle running within the bout (SSG-S) versus possession play only (SSG-P) on acute physiological and metabolic responses, perception of effort, and performance. Methods: Ten young elite male soccer players (age 18.6 [1.9] y) performed two 5vs5 SSG formats (SSG-S and SSG-P) consisting of 4 × 4 minutes with 1 minute of passive recovery between bouts, 2 times each, once a week, and in a randomized order. Heart rate, blood lactate concentration, and rating of perceived exertion were assessed as indices of internal workload. Total and relative distances, distance at moderate and high speed, distances traveled in accelerations (≥2 m·s−2) and decelerations (≤−2 m·s−2; DDEC), and average metabolic power were chosen as indices of external workload and collected with a 10-Hz portable global positioning system device. Results: Total distance, distances traveled in acceleration, distances traveled in deceleration, average metabolic power (always P < .01 and g > 1.62—large effect), and distance at moderate speed (P = .03 and g = 0.84—large effect) were significantly higher in SSG-S than in SSG-P. Moreover, the SSG-S showed higher blood lactate concentration (P = .0001, g = 12.58—large effect) and rating of perceived exertion (P = .03, g = 1.14—large effect) values than SSG-P. No significant differences in peak heart rate, relative distance, and distance at high speed were found. Conclusions: Our study showed, in young competitive male soccer players, the effectiveness of an SSG format that includes shuttle running within each bout in the development of more relevant internal and external workloads. These experimental data should encourage coaches to use this new SSG regimen within the traditional weekly training program.

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Erik Wilmes, Bram J.C. Bastiaansen, Cornelis J. de Ruiter, Riemer J.K. Vegter, Michel S. Brink, Hidde Weersma, Edwin A. Goedhart, Koen A.P.M. Lemmink, and Geert J.P. Savelsbergh

Purpose: To determine the test–retest reliability of the recently developed Hip Load metric, evaluate its construct validity, and assess the differences with Playerload during football-specific short-distance shuttle runs. Methods: Eleven amateur football players participated in 2 identical experimental sessions. Each session included 3 different shuttle runs that were performed at 2 pace-controlled running intensities. The runs consisted of only running, running combined with kicks, and running combined with jumps. Cumulative Playerload and Hip Loads of the preferred and nonpreferred kicking leg were collected for each shuttle run. Test–retest reliability was determined using intraclass correlations, coefficients of variation, and Bland–Altman analyses. To compare the load metrics with each other, they were normalized to their respective values obtained during a 54-m run at 9 km/h. Sensitivity of each load metric to running intensity, kicks, and jumps was assessed using separate linear mixed models. Results: Intraclass correlations were high for the Hip Loads of the preferred kicking leg (.91) and the nonpreferred kicking leg (.96) and moderate for the Playerload (.87). The effects (95% CIs) of intensity and kicks on the normalized Hip Load of the kicking leg (intensity: 0.95 to 1.50, kicks: 0.36 to 1.59) and nonkicking leg (intensity: 0.96 to 1.53, kicks: 0.06 to 1.34) were larger than on the normalized Playerload (intensity: 0.12 to 0.25, kicks: 0.22 to 0.53). Conclusions: The inclusion of Hip Load in training load quantification may help sport practitioners to better balance load and recovery.

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Sarah M. Espinoza, Marla E. Eisenberg, Alina Levine, Iris W. Borowsky, Daheia J. Barr-Anderson, Melanie M. Wall, and Dianne Neumark-Sztainer

Background: We investigated the percentage of insufficiently active adolescents who became young adults meeting moderate to vigorous physical activity (MVPA) guidelines. We also explored adolescent psychosocial and environmental factors that predicted MVPA guideline adherence in young adulthood. Methods: Participants included N = 1001 adolescents (mean age = 14.1 y) reporting < 7 hours per week of MVPA and followed (8 y later) into young adulthood through Project EAT. We examined mean weekly hours of MVPA, MVPA change between adolescence and young adulthood, and the proportion of participants meeting MVPA guidelines in young adulthood. With sex-stratified logistic regression, we tested 11 adolescent psychosocial and environmental factors predicting meeting MVPA guidelines in young adulthood. Results: Overall, 55% of insufficiently active adolescents became young adults meeting MVPA guidelines. On average, participants reported 3.0 hours per week of MVPA, which improved to 3.8 hours per week in young adulthood. Among female participants, higher MVPA in adolescence and stronger feelings of exercise compulsion predicted greater odds of meeting adult MVPA guidelines (odds ratioMVPA = 1.18; odds ratiocompulsion = 1.13). Among female and male participants, perceived friend support for activity in adolescence predicted greater odds of meeting adult MVPA guidelines (odds ratiofemale = 1.12; odds ratiomale = 1.26). Conclusions: Insufficiently active adolescents can later meet adult guidelines. Interventions that increase perceived friend support for activity may benefit individuals across development.