TY - JOUR A1 - Krahé, Barbara A1 - Vanwesenbeeck, Ine T1 - Mapping an agenda for the study of youth sexual aggression in Europe: assessment, principles of good practice, and the multilevel analysis of risk factors JF - Journal of sexual aggression N2 - Sexual aggression is a serious threat to young people's sexual health in Europe, but establishing the exact scale of the problem has been hampered by a variety of conceptual and methodological problems. This article presents a framework for studying youth sexual aggression that addresses both prevalence and risk factors of victimisation and perpetration. It proposes a research tool to comprehensively assess the perpetration of, and victimisation by, sexual aggression that captures different coercive strategies, sexual acts, victim–perpetrator relations, and gender constellations. The instrument is rooted in a clear conceptual definition of sexual aggression and was pilot-tested in 10 countries of the European Union (EU). Furthermore, a list of good practice criteria is proposed to promote the quality and comparability of research on youth sexual aggression in Europe. A multilevel approach combining individual-level and country-level predictors of sexual aggression is outlined and illustrated with data from the pilot study in 10 countries. KW - Sexual aggression KW - sexual victimisation KW - youth KW - measurement KW - risk factors KW - Europe Y1 - 2016 U6 - https://doi.org/10.1080/13552600.2015.1066885 SN - 1355-2600 SN - 1742-6545 VL - 22 SP - 161 EP - 174 PB - Karger CY - Abingdon ER - TY - JOUR A1 - Borde, Ron A1 - Smith, Jordan J. A1 - Sutherland, Rachel A1 - Nathan, Nicole A1 - Lubans, David Revalds T1 - Methodological considerations and impact of school-based interventions on objectively measured physical activity in adolescents: a systematic review and meta-analysis JF - Obesity reviews : an official journal of the International Association for the Study of Obesity N2 - Objective: The aims of this systematic review and meta-analysis are (i) to determine the impact of school-based interventions on objectively measured physical activity among adolescents and (ii) to examine accelerometer methods and decision rule reporting in previous interventions. Methods: A systematic search was performed to identify randomized controlled trials targeting adolescents (age: >= 10 years), conducted in the school setting, and reporting objectively measured physical activity. Random effects meta-analyses were conducted to determine the pooled effects of previous interventions on total and moderate-to-vigorous physical activity. Potential moderators of intervention effects were also explored. Results: Thirteen articles met the inclusion criteria, and twelve were included in the meta-analysis. The pooled effects were small and non-significant for both total physical activity (standardized mean difference = 0.02 [95% confidence interval = -0.13 to 0.18]) and moderate-to-vigorous physical activity (standardized mean difference = 0.24 [95% confidence interval = -0.08 to 0.56]). Sample age and accelerometer compliance were significant moderators for total physical activity, with a younger sample and higher compliance associated with larger effects. Conclusion: Previous school-based physical activity interventions targeting adolescents have been largely unsuccessful, particularly for older adolescents. There is a need for more high-quality research using objective monitoring in this population. Future interventions should comply with best-practice recommendations regarding physical activity monitoring protocols. KW - Accelerometer KW - physical activity KW - school KW - youth Y1 - 2017 U6 - https://doi.org/10.1111/obr.12517 SN - 1467-7881 SN - 1467-789X VL - 18 SP - 476 EP - 490 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Negra, Yassine A1 - Chaabene, Helmi A1 - Sammoud, Senda A1 - Bouguezzi, Raja A1 - Abbes, Mohamed Aymen A1 - Hachana, Younes A1 - Granacher, Urs T1 - Effects of Plyometric Training on Physical Fitness in Prepuberal Soccer Athletes JF - International journal of sports medicine N2 - This study aimed at examining the effects of plyometric training on stable (SPT) vs. unstable (UPT) surfaces on physical fitness in prepuberal soccer players. Male athletes were randomly assigned to SPT (n = 18; age = 12.7 +/- 0.2 years) or UPT (n = 16; age = 12.2 +/- 0.5 years). Both groups conducted 3 regular soccer training sessions per week combined with either 2 SPT or UPT sessions. Assessment of jumping ability (countermovement jump [CMJ], and standing long jump [SLJ]), speed (10-m, 20-m, 30-m sprint), agility (Illinois agility test [IAT]), and balance (stable [SSBT], unstable [USBT] stork balance test; stable [SYBT], unstable [UYBT] Y balance test) was conducted pre-and post-training. An ANCO-VA model was used to test for between-group differences (SPT vs. UPT) at post-test using baseline values as covariates. No significant differences were found for CMJ height (p > 0.05, d = 0.54), SLJ (p > 0.05; d = 0.81), 10-m, 20-m, and 30-m sprint performances (p > 0.05, d = 0.00-0.24), IAT (p > 0.05, d = 0.48), and dynamic balance (SYBT and UYBT, both p > 0.05, d = 0.39, 0.08, respectively). Statistically significant between-group differences were detected for the USBT (p < 0.01, d = 1.86) and the SSBT (p < 0.01, d = 1.75) in favor of UPT. Following 8 weeks of SPT or UPT in prepuberal athletes, similar performance levels were observed in both groups for measures of jumping ability, speed, dynamic balance, and agility. However, if the goal is to additionally enhance static balance, UPT has an advantage over SPT. KW - youth KW - balance KW - jumping ability KW - athletic performance KW - football Y1 - 2017 U6 - https://doi.org/10.1055/s-0042-122337 SN - 0172-4622 SN - 1439-3964 VL - 38 SP - 370 EP - 377 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Negra, Yassine A1 - Chaabene, Helmi A1 - Sammoud, Senda A1 - Bouguezzi, Raja A1 - Mkaouer, Bessem A1 - Hachana, Younes A1 - Granacher, Urs T1 - EFFECTS OF PLYOMETRIC TRAINING ON COMPONENTS OF PHYSICAL FITNESS IN PREPUBERAL MALE SOCCER ATHLETES: THE ROLE OF SURFACE INSTABILITY JF - Journal of strength and conditioning research : the research journal of the NSCA N2 - Previous studies contrasted the effects of plyometric training (PT) conducted on stable vs. unstable surfaces on components of physical fitness in child and adolescent soccer players. Depending on the training modality (stable vs. unstable), specific performance improvements were found for jump (stable PT) and balance performances (unstable PT). In an attempt to combine the effects of both training modalities, this study examined the effects of PT on stable surfaces compared with combined PT on stable and unstable surfaces on components of physical fitness in prepuberal male soccer athletes. Thirty-three boys were randomly assigned to either a PT on stable surfaces (PTS; n = 17; age = 12.1 +/- 0.5 years; height = 151.6 +/- 5.7 cm; body mass = 39.2 +/- 6.5 kg; and maturity offset = 22.3 +/- 0.5 years) or a combined PT on stable and unstable surfaces (PTC; n = 16; age = 12.2 +/- 0.6 years; height = 154.6 +/- 8.1 cm; body mass = 38.7 +/- 5.0 kg; and maturity offset = 22.2 +/- 0.6 years). Both intervention groups conducted 4 soccer-specific training sessions per week combined with either 2 PTS or PTC sessions. Before and after 8 weeks of training, proxies of muscle power (e.g., countermovement jump [CMJ], standing long jump [SLJ]), muscle strength (e.g., reactive strength index [RSI]), speed (e.g., 20-m sprint test), agility (e.g., modified Illinois change of direction test [MICODT]), static balance (e.g., stable stork bal-ance test [SSBT]), and dynamic balance (unstable stork balance test [USBT]) were tested. An analysis of covariance model was used to test between-group differences (PTS vs. PTC) at posttest using baseline outcomes as covariates. No significant between-group differences at posttest were observed for CMJ (p > 0.05, d = 0.41), SLJ (p > 0.05, d = 0.36), RSI (p > 0.05, d = 0.57), 20-m sprint test (p > 0.05, d = 0.06), MICODT (p > 0.05, d = 0.23), and SSBT (p > 0.05, d = 0.20). However, statistically significant between-group differences at posttest were noted for the USBT (p < 0.01, d = 1.49) in favor of the PTC group. For most physical fitness tests (except RSI), significant pre-to-post improvements were observed for both groups (p < 0.01, d = 0.55-3.96). Eight weeks of PTS or PTC resulted in similar performance improvements in components of physical fitness except for dynamic balance. From a performance-enhancing perspective, PTC is recommended for pediatric strength and conditioning coaches because it produced comparable training effects as PTS on proxies of muscle power, muscle strength, speed, agility, static balance, and additional effects on dynamic balance. KW - youth KW - football KW - stretch-shortening cycle KW - athletic performance KW - balance Y1 - 2017 SN - 1064-8011 SN - 1533-4287 VL - 31 SP - 3295 EP - 3304 PB - Lippincott Williams & Wilkins CY - Philadelphia ER - TY - JOUR A1 - Puta, Christian A1 - Steidten, Thomas A1 - Baumbach, Philipp A1 - Woehrl, Toni A1 - May, Rico A1 - Kellmann, Michael A1 - Herbsleb, Marco A1 - Gabriel, Brunhild A1 - Weber, Stephanie A1 - Granacher, Urs A1 - Gabriel, Holger H. W. T1 - Standardized assessment of resistance training-Induced subjective symptoms and objective signs of immunological stress responses in young athletes JF - Frontiers in physiology N2 - From a health and performance-related perspective, it is crucial to evaluate subjective symptoms and objective signs of acute training-induced immunological responses in young athletes. The limited number of available studies focused on immunological adaptations following aerobic training. Hardly any studies have been conducted on resistance-training induced stress responses. Therefore, the aim of this observational study was to investigate subjective symptoms and objective signs of immunological stress responses following resistance training in young athletes. Fourteen (7 females and 7 males) track and field athletes with a mean age of 16.4 years and without any symptoms of upper or lower respiratory tract infections participated in this study. Over a period of 7 days, subjective symptoms using the Acute Recovery and Stress Scale (ARSS) and objective signs of immunological responses using capillary blood markers were taken each morning and after the last training session. Differences between morning and evening sessions and associations between subjective and objective parameters were analyzed using generalized estimating equations (GEE). In post hoc analyses, daily change-scores of the ARSS dimensions were compared between participants and revealed specific changes in objective capillary blood samples. In the GEE models, recovery (ARSS) was characterized by a significant decrease while stress (ARSS) showed a significant increase between morning and evening-training sessions. A concomitant increase in white blood cell count (WBC), granulocytes (GRAN) and percentage shares of granulocytes (GRAN%) was found between morning and evening sessions. Of note, percentage shares of lymphocytes (LYM%) showed a significant decrease. Furthermore, using multivariate regression analyses, we identified that recovery was significantly associated with LYM%, while stress was significantly associated with WBC and GRAN%. Post hoc analyses revealed significantly larger increases in participants' stress dimensions who showed increases in GRAN%. For recovery, significantly larger decreases were found in participants with decreases in LYM% during recovery. More specifically, daily change-scores of the recovery and stress dimensions of the ARSS were associated with specific changes in objective immunological markers (GRAN%, LYM%) between morning and evening-training sessions. Our results indicate that changes of subjective symptoms of recovery and stress dimensions using the ARSS were associated with specific changes in objectively measured immunological markers. KW - immune system KW - strength training KW - track and field KW - youth KW - Acute Recovery and Stress Scale (ARSS) Y1 - 2018 U6 - https://doi.org/10.3389/fphys.2018.00698 SN - 1664-042X VL - 9 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Slimani, Maamer A1 - Paravlic, Armin A1 - Granacher, Urs T1 - A Meta-Analysis to Determine Strength Training Related Dose-Response Relationships for Lower-Limb Muscle Power Development in Young Athletes JF - Frontiers in Physiology N2 - It is well-documented that strength training (ST) improves measures of muscle strength in young athletes. Less is known on transfer effects of ST on proxies of muscle power and the underlying dose-response relationships. The objectives of this meta-analysis were to quantify the effects of ST on lower limb muscle power in young athletes and to provide dose-response relationships for ST modalities such as frequency, intensity, and volume. A systematic literature search of electronic databases identified 895 records. Studies were eligible for inclusion if (i) healthy trained children (girls aged 6–11 y, boys aged 6–13 y) or adolescents (girls aged 12–18 y, boys aged 14–18 y) were examined, (ii) ST was compared with an active control, and (iii) at least one proxy of muscle power [squat jump (SJ) and countermovement jump height (CMJ)] was reported. Weighted mean standardized mean differences (SMDwm) between subjects were calculated. Based on the findings from 15 statistically aggregated studies, ST produced significant but small effects on CMJ height (SMDwm = 0.65; 95% CI 0.34–0.96) and moderate effects on SJ height (SMDwm = 0.80; 95% CI 0.23–1.37). The sub-analyses revealed that the moderating variable expertise level (CMJ height: p = 0.06; SJ height: N/A) did not significantly influence ST-related effects on proxies of muscle power. “Age” and “sex” moderated ST effects on SJ (p = 0.005) and CMJ height (p = 0.03), respectively. With regard to the dose-response relationships, findings from the meta-regression showed that none of the included training modalities predicted ST effects on CMJ height. For SJ height, the meta-regression indicated that the training modality “training duration” significantly predicted the observed gains (p = 0.02), with longer training durations (>8 weeks) showing larger improvements. This meta-analysis clearly proved the general effectiveness of ST on lower-limb muscle power in young athletes, irrespective of the moderating variables. Dose-response analyses revealed that longer training durations (>8 weeks) are more effective to improve SJ height. No such training modalities were found for CMJ height. Thus, there appear to be other training modalities besides the ones that were included in our analyses that may have an effect on SJ and particularly CMJ height. ST monitoring through rating of perceived exertion, movement velocity or force-velocity profile could be promising monitoring tools for lower-limb muscle power development in young athletes. KW - resistance training KW - muscle fitness KW - youth KW - meta-analysis KW - jump performance Y1 - 2018 U6 - https://doi.org/10.3389/fphys.2018.01155 SN - 1664-042X VL - 9 SP - 1 EP - 14 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Gebel, Arnd A1 - Lüder, Benjamin A1 - Granacher, Urs T1 - Effects of Increasing Balance Task Difficulty on Postural Sway and Muscle Activity in Healthy Adolescents JF - Frontiers in Physiology N2 - Evidence-based prescriptions for balance training in youth have recently been established. However, there is currently no standardized means available to assess and quantify balance task difficulty (BTD). Therefore, the objectives of this study were to examine the effects of graded BTD on postural sway, lower limb muscle activity and coactivation in adolescents. Thirteen healthy high-school students aged 16 to 17 volunteered to participate in this cross-sectional study. Testing involved participants to stand on a commercially available balance board with an adjustable pivot that allowed six levels of increasing task difficulty. Postural sway [i.e., total center of pressure (CoP) displacements] and lower limb muscle activity were recorded simultaneously during each trial. Surface electromyography (EMG) was applied in muscles encompassing the ankle (m. tibialis anterior, medial gastrocnemius, peroneus longus) and knee joint (m. vastus medialis, biceps femoris). The coactivation index (CAI) was calculated for ankle and thigh muscles. Repeated measures analyses of variance revealed a significant main effect of BTD with increasing task difficulty for postural sway (p < 0.001; d = 6.36), muscle activity (p < 0.001; 2.19 < d < 4.88), and CAI (p < 0.001; 1.32 < d < 1.41). Multiple regression analyses showed that m. tibialis anterior activity best explained overall CoP displacements with 32.5% explained variance (p < 0.001). The observed increases in postural sway, lower limb muscle activity, and coactivation indicate increasing postural demands while standing on the balance board. Thus, the examined board can be implemented in balance training to progressively increase BTD in healthy adolescents. KW - balance training KW - balance strategy KW - muscle coactivation KW - youth KW - training intensity Y1 - 2019 U6 - https://doi.org/10.3389/fphys.2019.01135 SN - 1664-042X VL - 10 IS - 9 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Ben Othman, Aymen A1 - Chaouachi, Anis A1 - Chaouachi, Mehdi A1 - Makhlouf, Issam A1 - Farthing, Jonathan P. A1 - Granacher, Urs A1 - Behm, David George T1 - Dominant and nondominant leg press training induce similar contralateral and ipsilateral limb training adaptations with children JF - Applied Physiology, Nutrition, and Metabolism N2 - Cross-education has been extensively investigated with adults. Adult studies report asymmetrical cross-education adaptations predominately after dominant limb training. The objective of the study was to examine unilateral leg press (LP) training of the dominant or nondominant leg on contralateral and ipsilateral strength and balance measures. Forty-two youth (10-13 years) were placed (random allocation) into a dominant (n = 15) or nondominant (n = 14) leg press training group or nontraining control (n = 13). Experimental groups trained 3 times per week for 8 weeks and were tested pre-/post-training for ipsilateral and contralateral 1-repetition maximum (RM) horizontal LP, maximum voluntary isometric contraction (MVIC) of knee extensors (KE) and flexors (KF), countermovement jump (CMJ), triple hop test (THT), MVIC strength of elbow flexors (EF) and handgrip, as well as the stork and Y balance tests. Both dominant and nondominant LP training significantly (p < 0.05) increased both ipsilateral and contralateral lower body strength (LP 1RM (dominant: 59.6%-81.8%; nondominant: 59.5%-96.3%), KE MVIC (dominant: 12.4%-18.3%; nondominant: 8.6%-18.6%), KF MVIC (dominant: 7.9%-22.3%; nondominant: nonsignificant-3.8%), and power (CMJ: dominant: 11.1%-18.1%; nondominant: 7.7%-16.6%)). The exception was that nondominant LP training demonstrated a nonsignificant change with the contralateral KF MVIC. Other significant improvements were with nondominant LP training on ipsilateral EF 1RM (6.2%) and THT (9.6%). There were no significant changes with EF and handgrip MVIC. The contralateral leg stork balance test was impaired following dominant LP training. KF MVIC exhibited the only significant relative post-training to pretraining (post-test/pre-test) ratio differences between dominant versus nondominant LP cross-education training effects. In conclusion, children exhibit symmetrical cross-education or global training adaptations with unilateral training of dominant or nondominant upper leg. KW - resistance training KW - cross-education KW - youth KW - strength KW - power KW - balance Y1 - 2019 U6 - https://doi.org/10.1139/apnm-2018-0766 SN - 1715-5312 SN - 1715-5320 VL - 44 IS - 9 SP - 973 EP - 984 PB - NRC Research Press CY - Ottawa ER - TY - JOUR A1 - Negra, Yassine A1 - Chaabene, Helmi A1 - Fernandez-Fernandez, Jaime A1 - Sammoud, Senda A1 - Bouguezzi, Raja A1 - Prieske, Olaf A1 - Granacher, Urs T1 - Short-term plyometric Jump training improves repeated-sprint ability in prepuberal male soccer players JF - Journal of strength and conditioning research : the research journal of the NSCA N2 - This study examined the effects of a short-term (i.e., 8 weeks) combined horizontal and vertical plyometric jump training (PJT) program in combination with regular soccer-specific training as compared with soccer-specific training only on jump and change of direction (CoD) performances, speed, and repeated-sprint ability (RSA) in prepuberal male soccer players. Twenty-four players were recruited and randomly assigned to either a PJT group (PJT(G); n = 13; 12.7 +/- 0.2 years) or an active control group (CONG; n = 11; 12.7 +/- 0.2 years). The outcome measures included tests for the assessment of jump performance (drop jump from 20- to 40-cm height [DJ20 and DJ40] and 3-hop test [THT]), speed (20-m sprint), CoD (T-test), and RSA (20-m repeated shuttle sprint). Data were analyzed using magnitude-based inferences. Within-group analyses revealed large performance improvements in the T-test (d = -1.2), DJ20 (d = 3.7), DJ40 (d = 3.6), THT (d = 0.6), and the RSA(total) (d = -1.6) in the PJT(G). Between-group analyses showed greater performance improvements in the T-test (d = -2.9), 20-m sprint time (d = -2.0), DJ20 (d = 2.4), DJ40 (d = 2.0), THT (d = 1.9), RSA(best) (d = -1.9), and the RSA(total) (d = -1.9) in the PJT(G) compared with CONG. Eight weeks of an in-season PJT in addition to regular soccer-specific training induced larger increases in measures of physical fitness in prepuberal male soccer players compared with regular soccer-specific training only. More specifically, PJT was effective in improving RSA performance. KW - youth KW - stretch-shortening cycle KW - athletic performance KW - soccer Y1 - 2020 U6 - https://doi.org/10.1519/JSC.0000000000002703 SN - 1064-8011 SN - 1533-4287 VL - 34 IS - 11 SP - 3241 EP - 3249 PB - Lippincott Williams & Wilkins CY - Philadelphia ER - TY - JOUR A1 - Gebel, Arnd A1 - Lehmann, Tim A1 - Granacher, Urs T1 - Balance task difficulty affects postural sway and cortical activity in healthy adolescents JF - Experimental brain research N2 - Electroencephalographic (EEG) research indicates changes in adults' low frequency bands of frontoparietal brain areas executing different balance tasks with increasing postural demands. However, this issue is unsolved for adolescents when performing the same balance task with increasing difficulty. Therefore, we examined the effects of a progressively increasing balance task difficulty on balance performance and brain activity in adolescents. Thirteen healthy adolescents aged 16-17 year performed tests in bipedal upright stance on a balance board with six progressively increasing levels of task difficulty. Postural sway and cortical activity were recorded simultaneously using a pressure sensitive measuring system and EEG. The power spectrum was analyzed for theta (4-7 Hz) and alpha-2 (10-12 Hz) frequency bands in pre-defined frontal, central, and parietal clusters of electrocortical sources. Repeated measures analysis of variance (rmANOVA) showed a significant main effect of task difficulty for postural sway (p < 0.001; d = 6.36). Concomitantly, the power spectrum changed in frontal, bilateral central, and bilateral parietal clusters. RmANOVAs revealed significant main effects of task difficulty for theta band power in the frontal (p < 0.001, d = 1.80) and both central clusters (left: p < 0.001, d = 1.49; right: p < 0.001, d = 1.42) as well as for alpha-2 band power in both parietal clusters (left: p < 0.001, d = 1.39; right: p < 0.001, d = 1.05) and in the central right cluster (p = 0.005, d = 0.92). Increases in theta band power (frontal, central) and decreases in alpha-2 power (central, parietal) with increasing balance task difficulty may reflect increased attentional processes and/or error monitoring as well as increased sensory information processing due to increasing postural demands. In general, our findings are mostly in agreement with studies conducted in adults. Similar to adult studies, our data with adolescents indicated the involvement of frontoparietal brain areas in the regulation of postural control. In addition, we detected that activity of selected brain areas (e.g., bilateral central) changed with increasing postural demands. KW - balance KW - postural control KW - EEG KW - Theta KW - Alpha-2 KW - ICA KW - youth Y1 - 2020 U6 - https://doi.org/10.1007/s00221-020-05810-1 SN - 0014-4819 SN - 1432-1106 VL - 238 IS - 5 SP - 1323 EP - 1333 PB - Springer CY - New York ER -