The recent literature delineates resistance training in children and adolescents to be effective and safe. However, only little is known about the transfer of achieved strength gains to athletic performance. The present meta-analysis revealed a combined mean effect size for motor skill types jumping, running, and throwing of 0.52 (95% CI: 0.33-0.71). Effect sizes for each of aforementioned skill types separately were 0.54 (95% CI: 0.34-0.74), 0.53 (95% CI: 0.23-0.83), and 0.99 (95% CI: 0.19-1.79) respectively. Furthermore, it could be shown that younger subjects and nonathletes showed higher gains in motor performance following resistance training than their counterparts and that specific resistance training regimes were not advantageous over traditional resistance training programs. Finally, a positive dose response relationship for "intensity" could be found in subgroups using traditional training regimens. These results emphasize that resistance training provides an effective way for enhancing motor performance in children and adolescents.

Little is known about the prevalence and motives of supplement use among elite young athletes who compete on national and international levels. Therefore, the current survey was performed to assess information regarding the past and present use of dietary supplements among 164 elite young athletes (16.6 +/- 3.0 years of age). A 5-page questionnaire was designed to assess their past and present (last 4 weeks) use of vitamins, minerals, carbohydrate, protein, and fat supplements; sport drinks; and other ergogenic aids. Furthermore, information about motives, sources of advice, supplement sources, and supplement contamination was assessed. Eighty percent of all athletes reported using at least 1 supplement, and the prevalence of use was significantly higher in older athletes (p < .05). Among supplement users, minerals, vitamins, sport drinks, energy drinks, and carbohydrates were most frequently consumed. Only a minority of the athletes declared that they used protein/amino acids, creatine, or other ergogenic aids. Major motives for supplement use were health related, whereas performance enhancement and recommendations by others were less frequently reported. Supplements were mainly obtained from parents or by athletes themselves and were mostly purchased in pharmacies, supermarkets, and health-food stores. Among all athletes, only 36% were aware of the problem of supplement contamination. The survey shows that supplement use is common and widespread among German elite young athletes. This stands in strong contrast to recommendations by leading sport organizations against supplement use by underage athletes.

The results of our analysis indicate that the ability to gain muscular strength seems to increase with age and maturational status, but there is no noticeable boost during puberty. Furthermore, study duration and the number of performed sets were found to have a positive impact on the outcome.

This study aimed to investigate the biological response to hypoxia as a stimulus, as well as exercise- and vibration-induced shear stress, which is known to induce angiogenesis. Twelve male cyclists (27.8 +/- 5.4 yr) participated in this study. Each subject completed four cycle training sessions under normal conditions (NC) without vibration, NC with vibration, normobaric hypoxic conditions (HC) without vibration, and HC with vibration. Each session lasted 90 min, and sessions were held at weekly intervals in a randomized order. Five blood samples (pretraining and 0 h post-, 0.5 h post-, 1 h post-, and 4 h posttraining) were taken from each subject at each training session. Hypoxia was induced by a normobaric hypoxic chamber with an altitude of 2,500 m. The mechanical forces (cycling with or without vibration) were induced by a cycling ergometer. The parameters VEGF, endostatin, and matrix metalloproteinases (MMPs) were analyzed using the ELISA method. VEGF showed a significant increase immediately after the exercise only with exogenously induced vibrations, as calculated with separate ANOVA analysis. Endostatin increased after training under all conditions. Western blot analysis was performed for the determination of endostatin corresponding to the 22-kDa cleavage product of collagen XVIII. This demonstrated elevated protein content for endostatin at 0 h postexercise. MMP-2 increased in three of the four training conditions. The exception was NC with vibration. MMP-9 reached its maximum level at 4 h postexercise. In conclusion, the results support the contention that mechanical stimuli differentially influence factors involved in the induction of angiogenesis. These findings may contribute to a broader understanding of angiogenesis.

High-intensity interval training (HIIT) in junior and adult soccer has been shown to improve oxygen uptake (VO₂) and enhance soccer performance. The main purpose of this study was to examine the short term effects of a 5-week HIIT vs. high-volume training (HVT) program in 14-year-old soccer players regarding the effects on VO₂max and 1,000-m time (T₁₀₀₀) and on sprinting and jumping performance. In a 5-week period, 19 male soccer players with a mean (SD) age of 13.5 ± 0.4 years performed HIIT at close to ~90% of maximal heart rate. The HVT intensity was set at 60-75% of maximal heart rate. VO₂max increased significantly (7.0%) from pre to post in HIIT but not after HVT. T₁₀₀₀ decreased significantly after HIIT (~-10 vs. ~-5 seconds in HVT). Sprint performance increased significantly in both groups from pre to posttesting without any changes in jumping performance.