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Benjamin Drury, Thomas Green, Rodrigo Ramirez-Campillo, and Jason Moran

Purpose: This study examined the effects of a 6-week Nordic hamstring exercise (NHE) program in youth male soccer players of less mature (pre–peak height velocity [PHV]) or more mature (mid/post-PHV) status. Methods: Forty-eight participants were separated into pre-PHV (11.0 [0.9] y) or mid/post-PHV (13.9 [1.1]) groups and further divided into experimental (EXP) and control groups with eccentric hamstring strength assessed (NordBord) both before and after the training program. Participants in the EXP groups completed a periodized NHE program performed once or twice weekly over a 6-week period. Results: The NHE program resulted in moderate and small increases in relative eccentric hamstring strength (in newtons per kilogram) in the pre-PHV EXP (d = 0.83 [0.03–1.68]) and mid-PHV EXP (d = 0.53 [−0.06 to 1.12]) groups, respectively. Moderate increases in the same measure were also seen in the between-groups analyses in the pre-PHV (d = 1.03 [0.23–1.84]) and mid-PHV (d = 0.87 [0.22–1.51]) groups, with a greater effect observed in the former. Conclusion: The results from this study demonstrate that a 6-week NHE program can improve eccentric hamstring strength in male youth soccer players, with less-mature players achieving mostly greater benefits. The findings from this study can aid in the training prescription of NHE in youth male soccer players.

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Helmi Chaabene, Yassine Negra, Jason Moran, Olaf Prieske, Senda Sammoud, Rodrigo Ramirez-Campillo, and Urs Granacher

Purpose: This study examined the effects of an 8-week Nordic hamstring exercise (NHE) training on components of physical performance in young female handball players. Methods: Participants were allocated to an experimental group (EG; n = 10; age: 15.9 [0.2] y) and a control group (CG; n = 9; age: 15.9 [0.3] y). The EG performed NHE (2–3 sessions/wk) in replacement of some handball-specific drills, whereas the CG followed regular handball training. Pretraining and posttraining tests were carried out for the assessment of sprint speed (5 m, 10 m, and 20 m), jump performance (countermovement jump [CMJ] height), change-of-direction (t test), and repeated-sprint ability (RSA total time [RSAtotal], RSA best time [RSAbest], and RSA fatigue index [RSAFI]). Data were analyzed using magnitude-based inferences. Results: Within-group analyses for the EG showed moderate performance improvements for 5, 10, and 20 m (effect size [ES] = 0.68–0.82), t test (ES = 0.74), and CMJ (ES = 0.85). Trivial to small improvements were observed for RSA (ES = −0.06 to 0.35). For the CG, within-group outcomes showed performance decrements with moderate (t test [ES = 0.71]), small (5 m [ES = 0.46] and RSAbest [ES = 0.20]), and trivial magnitude (10 m [ES = 0.10], 20 m [ES = 0.16], and RSAtotal [ES = 0.00]). Furthermore, trivial to small performance improvements were found for CMJ (ES = 0.10) and RSAFI (ES = 0.5). Between-group analyses revealed small to large effects in favor of EG for 5 m (ES = 1.07), 10 m (ES = 0.66), 20 m (ES = 0.53), t test (ES = 1.38), and RSA (ES = 0.68–0.78). A trivial between-group difference was demonstrated for CMJ (ES = −0.01). Conclusions: The NHE training intervention, in replacement of some handball-specific drills, was more effective than regular handball training in improving physical performance (ie, linear sprint time, jumping, change-of-direction, and RSA) in young female handball players.

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Jason Moran, Gavin R.H. Sandercock, Rodrigo Ramírez-Campillo, Oliver Todd, Jay Collison, and Dave A. Parry

Purpose:

The purpose of this intervention study was to investigate if a low-dose of plyometric training (PT) could improve sprint and jump performance in groups of different maturity status.

Method:

Male youth field hockey players were divided into Pre-PHV (from -1 to -1.9 from PHV; Experimental: n = 9; Control = 12) and Mid-PHV (0 to +0.9 from PHV; Experimental: n = 8; Control = 9) groups. Participants in the experimental groups completed 60 foot contacts, twice-weekly for 6 weeks.

Results:

PT exerted a positive effect (effect size: 0.4 [-0.4–1.2]) on 10 m sprint time in the experimental Mid-PHV group but this was less pronounced in the Pre-PHV group (0.1 [-0.6–0.9]). Sprint time over 30 m (Mid-PHV: 0.1 [-0.8–0.9]; Pre-PHV: 0.1 [-0.7–0.9]) and CMJ (Mid-PHV: 0.1 [-0.8–0.9]; Pre-PHV: 0.0 [-0.7–0.8]) was maintained across both experimental groups. Conversely, the control groups showed decreased performance in most tests at follow up. Between-group analysis showed positive effect sizes across all performance tests in the Mid-PHV group, contrasting with all negative effect sizes in the Pre-PHV group.

Conclusion:

These results indicate that more mature hockey players may benefit to a greater extent than less mature hockey players from a low-dose PT stimulus. Sixty foot contacts, twice per week, seems effective in improving short sprint performance in Mid-PHV hockey players.

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Lucas A. Pereira, Andrew A. Flatt, Rodrigo Ramirez-Campillo, Irineu Loturco, and Fabio Y. Nakamura

Purpose:

To compare the LnRMSSD and the LnRMSSD:RR values obtained during a 5-min stabilization period with the subsequent 5-min criterion period and to determine the time course for LnRMSSD and LnRMSSD:RR stabilization at 1-min analysis in elite team-sport athletes.

Participants:

35 elite futsal players (23.9 ± 4.5 y, 174.2 ± 4.0 cm, 74.0 ± 7.5 kg, 1576.2 ± 396.3 m in the Yo-Yo test level 1).

Methods:

The RR-interval recordings were obtained using a portable heart-rate monitor continuously for 10 min in the seated position. The 2 dependent variables analyzed were LnRMSSD and LnRMSSD:RR. To calculate the magnitude of the differences between time periods, effect-size (ES) analysis was conducted. To assess the levels of agreement, intraclass correlation coefficients (ICC) and Bland-Altman plots were used.

Results:

The LnRMSSD and LnRMSSD:RR values obtained during the stabilization period (0–5 min) presented very large to nearly perfect ICCs with the values obtained during the criterion period (5–10 min), with trivial ESs. In the ultra-short-term analysis (ie, 1-min segments) the data showed slightly less accurate results, but only trivial to small differences with very large to nearly perfect ICCs were found.

Conclusion:

LnRMSSD and LnRMSSD:RR can be recorded in 5 min without traditional stabilization periods under resting conditions in team-sport athletes. The ultra-short-term analysis (1 min) also revealed acceptable levels of agreement with the criterion.

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Helmi Chaabene, Yassine Negra, Senda Sammoud, Jason Moran, Rodrigo Ramirez-Campillo, Urs Granacher, and Olaf Prieske

Purpose: To examine the effects of balance exercises conducted prior to complex training (bCT) versus complex training (CT) only on measures of physical fitness in young female elite handball players. Methods: Participants aged 17 years were randomly assigned to bCT (n = 11) or CT (n = 12). The 2 training interventions lasted 8 weeks with 2 sessions per week in replacement of some technical/tactical handball exercises and were matched for total training volume. Before and after training, tests were performed for the evaluation of proxies of muscle power (countermovement jump height, standing long-jump distance, and reactive strength index), muscle strength (back half-squat 1-repetition maximum), dynamic balance (Y-balance test), linear sprint speed (20-m sprint test), and change-of-direction speed (T test). Results: Two-factor repeated-measures analysis of variance revealed significant group × time interactions for the reactive strength index (d = 0.99, P = .03) and Y-balance test score (d = 1.32, P < .01). Post hoc analysis indicated significant pre–post reactive strength index improvements in CT (d = 0.69, P = .04) only. For the Y-balance test, significant pre–post increases were found in bCT (d = 0.71, P = .04) with no significant changes in CT (d = 0.61, P = .07). In addition, significant main effects of time were observed for half-squat 1-repetition maximum, countermovement jump, standing long jump, and T test performance (d = 1.50 to 3.10, P < .05). Conclusions: Both bCT and CT interventions were effective in improving specific measures of physical fitness in young elite female handball players. If the training goal is to improve balance in addition, balance exercises can be conducted within a CT training session and prior to CT exercises.

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Mehrez Hammami, Rodrigo Ramirez-Campillo, Nawel Gaamouri, Gaith Aloui, Roy J. Shephard, and Mohamed Souhaiel Chelly

Purpose: To analyze the effects of a 9-week plyometric training program on the sprint times (5, 10, 20, and 30 m), change-of-direction speed (modified T test and modified Illinois test), jumping (squat jump, countermovement jump, countermovement jump with arms, and horizontal 5-jump test), upper-body strength (right and left handgrip, back extensor strength, and medicine ball throw), and balance (Y and stork balance tests) of female handball players. Methods: Athletes were randomly divided into experimental (n = 21; age = 13.5 [0.3] y) and control (n = 20; age = 13.3 [0.3] y) groups. Training exercises and matches were performed together, but the experimental group replaced a part of their normal regimen by biweekly upper- and lower-limb plyometric training. Results: Both groups improved performance, but to a greater extent in the experimental group compared with controls for 20- and 30-m sprint times (Δ% = 9.6, P < .05, d = 0.557 and Δ% = 20.9, P < .001, d = 1.07, respectively), change of direction (T test: P < .01, Δ% = 14.5, d = 0.993 and Illinois test: P < .01, Δ% = 7.9, d = 0.769), vertical and horizontal jumping (P < .05), all measures of upper-limb strength (P < .001), and left-leg stork balance (P < .001, Δ% = 49.9, d = 1.07). Conclusions: A plyometric training program allows female junior handball players to improve important components of their physical performance.

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Cristian Jaque, Phillip Véliz, Rodrigo Ramirez-Campillo, Jason Moran, Paulo Gentil, and Jorge Cancino

The authors compared the effects of bodyweight resistance training at moderate- or high-speed conditions on muscle power, velocity of movement, and functional performance in older females. In a randomized, single-blinded noncontrolled trial, participants completed 12 weeks (three sessions/week) of bodyweight resistance training at high (n = 14; age = 70.6 ± 4.3 years) or moderate (n = 12; age = 72.8 ± 4.2 years) speeds. Data were analyzed with an analysis of variance (Group × Time) with α level set at <.05. After the intervention, timed up and go test performance (p < .05) and the rising from a chair test mean (22.4%) and maximal velocity (28.5%), mean (24.4%) and maximal power (27.7%), normalized mean (25.1%), and normalized maximal power (28.5%) increased in the high-speed group (p < .05). However, the moderate-speed group achieved no improvements (Δ6.7–14.4%; p > .2). The authors conclude that high-speed bodyweight resistance training is an effective and economically practical strategy to improve the functional capacity of older women relevant to daily life activities.

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Felipe García-Pinillos, Carlos Lago-Fuentes, Pedro A. Latorre-Román, Antonio Pantoja-Vallejo, and Rodrigo Ramirez-Campillo

Context: Plyometric training promotes a highly effective neuromuscular stimulus to improve running performance. Jumping rope (JR) involves mainly foot muscles and joints, due to the quick rebounds, and it might be considered a type of plyometric training for improving power and stiffness, some of the key factors for endurance-running performance. Purpose: To determine the effectiveness of JR during the warm-up routine of amateur endurance runners on jumping performance, reactivity, arch stiffness, and 3-km time-trial performance. Methods: Athletes were randomly assigned to an experimental (n = 51) or control (n = 45) group. Those from the control group were asked to maintain their training routines, while athletes from the experimental group had to modify their warm-up routines, including JR (2–4 sessions/wk, with a total time of 10–20 min/wk) for 10 weeks. Physical tests were performed before (pretest) and after (posttest) the intervention period and included jumping performance (countermovement-jump, squat-jump, and drop-jump tests), foot-arch stiffness, and 3-km time-trial performance. Reactive strength index (RSI) was calculated from a 30-cm drop jump. Results : The 2 × 2 analysis of variance showed significant pre–post differences in all dependent variables (P < .001) for the experimental group. No significant changes were reported in the control group (all P ≥ .05). Pearson correlation analysis revealed a significant relationship between Δ3-km time trial and ΔRSI (r = −.481; P < .001) and ΔStiffness (r = −.336; P < .01). The linear-regression analysis showed that Δ3-km time trial was associated with ΔRSI and ΔStiffness (R 2 = .394; P < .001). Conclusions : Compared with a control warm-up routine prior to endurance-running training, 10 weeks (2–4 times/wk) of JR training, in place of 5 minutes of regular warm-up activities, was effective in improving 3-km time-trial performance, jumping ability, RSI, and arch stiffness in amateur endurance runners. Improvements in RSI and arch stiffness were associated with improvements in 3-km time-trial performance.

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Yassine Negra, Helmi Chaabene, Senda Sammoud, Olaf Prieske, Jason Moran, Rodrigo Ramirez-Campillo, Ali Nejmaoui, and Urs Granacher

Purpose: To examine the effects of loaded (LPJT) versus unloaded plyometric jump training (UPJT) programs on measures of muscle power, speed, change of direction (CoD), and kicking-distance performance in prepubertal male soccer players. Methods: Participants (N = 29) were randomly assigned to a LPJT group (n = 13; age = 13.0 [0.7] y) using weighted vests or UPJT group (n = 16; age = 13.0 [0.5] y) using body mass only. Before and after the intervention, tests for the assessment of proxies of muscle power (ie, countermovement jump, standing long jump); speed (ie, 5-, 10-, and 20-m sprint); CoD (ie, Illinois CoD test, modified 505 agility test); and kicking-distance were conducted. Data were analyzed using magnitude-based inferences. Results: Within-group analyses for the LPJT group showed large and very large improvements for 10-m sprint time (effect size [ES] = 2.00) and modified 505 CoD (ES = 2.83) tests, respectively. For the same group, moderate improvements were observed for the Illinois CoD test (ES = 0.61), 5- and 20-m sprint time test (ES = 1.00 for both the tests), countermovement jump test (ES = 1.00), and the maximal kicking-distance test (ES = 0.90). Small enhancements in the standing long jump test (ES = 0.50) were apparent. Regarding the UPJT group, small improvements were observed for all tests (ES = 0.33–0.57), except 5- and 10-m sprint time (ES = 1.00 and 0.63, respectively). Between-group analyses favored the LPJT group for the modified 505 CoD (ES = 0.61), standing long jump (ES = 0.50), and maximal kicking-distance tests (ES = 0.57), but not for the 5-m sprint time test (ES = 1.00). Only trivial between-group differences were shown for the remaining tests (ES = 0.00–0.09). Conclusion: Overall, LPJT appears to be more effective than UPJT in improving measures of muscle power, speed, CoD, and kicking-distance performance in prepubertal male soccer players.

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Guillermo Mendez-Rebolledo, Romina Figueroa-Ureta, Fernanda Moya-Mura, Eduardo Guzmán-Muñoz, Rodrigo Ramirez-Campillo, and Rhodri S. Lloyd

Context: Few reports have analyzed the effects of neuromuscular (NM) training programs on the injury incidence among youth female track-and-field athletes. Objective: To determine the effects of NM training on reducing lower limb injury incidence and to establish its effects on countermovement jump performance, balance, 30-m sprint, and joint position sense in youth female track-and-field athletes. Design: Single-blind, randomized controlled clinical trial. Setting:Sports research laboratory. Participants: Twenty-two female athletes were allocated into 2 groups: Conventional (CONV) training (n = 11; age = 15.3 [2.1] y) and NM training (n = 11; age = 15.0 [2.7] y). Interventions: Interventions were performed during the preseason of 6 weeks. The CONV training included anaerobic, strength, and aerobic training. The NM training consisted of a multicomponent program that integrated jumps, landings, and running with strength, endurance, agility, balance, and CORE training. Main Outcome Measures: A follow-up of the cohorts was carried out through the evaluation of lower limb injuries (main outcome) during a regular season (weeks 7–18). Secondary outcomes were measured before and after the intervention: Y-balance test, active joint repositioning, ground reaction force, and countermovement jump height. Results: The injury incidence rate was 17.89 injuries per 1000 hours athlete-exposure in CONV training, and 6.58 in NM training (relative risk = 0.38; 95% confidence interval,  0.18 to 0.82; P = .044). Particularly, the medial tibial stress syndrome incidence rate was 5.96 injuries per 1000 hours athlete-exposure in CONV training and 0.82 in NM training (relative risk = 0.17; 95% confidence interval, 0.02 to 1.12; P = .012). In addition, a significant training × time interaction was noted, favoring improvements in 30-m sprint and countermovement jump height after NM. Conclusion: The NM training may improve youth female athlete’s physical fitness and reduce their injury relative risk of medial tibial stress syndrome injury.