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Thomas Muehlbauer, Claude Mettler, Ralf Roth and Urs Granacher

The purpose of this study was to compare static balance performance and muscle activity during one-leg standing on the dominant and nondominant leg under various sensory conditions with increased levels of task difficulty. Thirty healthy young adults (age: 23 ± 2 years) performed one-leg standing tests for 30 s under three sensory conditions (ie, eyes open/firm ground; eyes open/foam ground [elastic pad on top of the balance plate]; eyes closed/firm ground). Center of pressure displacements and activity of four lower leg muscles (ie, m. tibialis anterior [TA], m. soleus [SOL], m. gastrocnemius medialis [GAS], m. peroneus longus [PER]) were analyzed. An increase in sensory task difficulty resulted in deteriorated balance performance (P < .001, effect size [ES] = .57−2.54) and increased muscle activity (P < .001, ES = .50−1.11) for all but two muscles (ie, GAS, PER). However, regardless of the sensory condition, one-leg standing on the dominant as compared with the nondominant limb did not produce statistically significant differences in various balance (P > .05, ES = .06−.22) and electromyographic (P > .05, ES = .03−.13) measures. This indicates that the dominant and the nondominant leg can be used interchangeably during static one-leg balance testing in healthy young adults.

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Urs Granacher, Andre Lacroix, Katrin Roettger, Albert Gollhofer and Thomas Muehlbauer

This study investigated associations between variables of trunk muscle strength (TMS), spinal mobility, and balance in seniors. Thirty-four seniors (sex: 18 female, 16 male; age: 70 ± 4 years; activity level: 13 ± 7 hr/week) were tested for maximal isometric strength (MIS) of the trunk extensors, flexors, lateral flexors, rotators, spinal mobility, and steady-state, reactive, and proactive balance. Significant correlations were detected between all measures of TMS and static steady-state balance (r = .43−.57, p < .05). Significant correlations were observed between specific measures of TMS and dynamic steady-state balance (r = .42−.55, p < .05). No significant correlations were found between all variables of TMS and reactive/proactive balance and between all variables of spinal mobility and balance. Regression analyses revealed that TMS explains between 1–33% of total variance of the respective balance parameters. Findings indicate that TMS is related to measures of steady-state balance which may imply that TMS promoting exercises should be integrated in strength training for seniors.

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Olaf Prieske, Helmi Chaabene, Christian Puta, David G. Behm, Dirk Büsch and Urs Granacher

Purpose: To examine the effects of drop height on drop-jump (DJ) performance and on associations between DJ and horizontal-jump/sprint performances in adolescent athletes. Methods: Male (n = 119, 2.5 [0.6] y post-peak-height velocity) and female (n = 120, 2.5 [0.5] y post-peak-height velocity) adolescent handball players (national level) performed DJs in randomized order using 3 drop heights (20, 35, and 50 cm). DJ performance (jump height, reactive strength index [RSI]) was analyzed using the Optojump Next system. In addition, correlations were computed between DJ height and RSI with standing-long-jump and 20-m linear-sprint performances. Results: Statistical analyses revealed medium-size main effects of drop height for DJ height and RSI (P < .001, 0.63 ≤ d ≤ 0.71). Post hoc tests indicated larger DJ heights from 20 to 35 and 35 to 50 cm (P ≤ .031, 0.33 ≤ d ≤ 0.71) and better RSI from 20- to 35-cm drop height (P < .001, d = 0.77). No significant difference was found for RSI between 35- and 50-cm drop height. Irrespective of drop height, associations of DJ height and RSI were small with 5-m-split time (−.27 ≤ r ≤ .05), medium with 10-m-split time (−.44 ≤ r ≤ .14), and medium to large with 20-m sprint time and standing-long-jump distance (−.57 ≤ r ≤ .22). Conclusions: The present findings indicate that, irrespective of sex, 35-cm drop heights are best suited to induce rapid and powerful DJ performance (ie, RSI) during reactive strength training in elite adolescent handball players. Moreover, training-related gains in DJ performance may at least partly translate to gains in horizontal jump and longer sprint distances (ie, ≥20-m) and/or vice versa in male and female elite adolescent athletes, irrespective of drop height.

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Raouf Hammami, Anis Chaouachi, Issam Makhlouf, Urs Granacher and David G. Behm

Balance, strength and power relationships may contain important information at various maturational stages to determine training priorities.

Purpose:

The objective was to examine maturity-specific relationships of static/dynamic balance with strength and power measures in young male athletes.

Methods:

Soccer players (N = 130) aged 10–16 were assessed with the Stork and Y balance (YBT) tests. Strength/power measures included back extensor muscle strength, standing long jump (SLJ), countermovement jump (CMJ), and 3-hop jump tests. Associations between balance with strength/power variables were calculated according to peak-height-velocity (PHV).

Results:

There were significant medium-large sized correlations between all balance measures with back extensor strength (r = .486–.791) and large associations with power (r = .511–.827). These correlation coefficients were significantly different between pre-PHV and circa PHV as well as pre-PHV and post-PHV with larger associations in the more mature groups. Irrespective of maturity-status, SLJ was the best strength/power predictor with the highest proportion of variance (12–47%) for balance (i.e., Stork eyes opened) and the YBT was the best balance predictor with the highest proportion of variance (43–78%) for all strength/power variables.

Conclusion:

The associations between balance and muscle strength/power measures in youth athletes that increase with maturity may imply transfer effects from balance to strength/power training and vice versa in youth athletes.

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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 (EG; n=10; age: 15.9 ± 0.2 years) and a control group (CG; n=9; age: 15.9 ± 0.3 years). The EG performed NHE (2-3 sessions/week) in replacement of some handball-specific drills whereas the CG followed regular handball training. Pre- and post-training, tests were carried-out for the assessment of sprint speed (5 m, 10 m, 20 m), jump performance (countermovement jump [CMJ] height), change-of-direction (CoD [T-test]), and repeated-sprint-ability (RSA total-time [RSAtotal], RSA best-time [RSAbest], RSA fatigue-index [RSAFI]). Data were analyzed using magnitude-based inferences.

Results:

Within-group analyses for the EG showed moderate performance improvements for 5 m, 10 m, 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=-0.06-0.35). 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]). Further, 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 to 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 (i.e., linear sprint-time, jumping, CoD, and RSA) in young female handball players.

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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.