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Possible diff erences in the physical values related to characteristics of the age group and the play positions in soccer. The aims to analyze the isokinetic muscle strength profi les, anthropometric, neuromuscular and cardiovascular characteristics, comparing age, categories and play positions. 105 players divided into U-17, U-20, Professional and six play positions. The isokinetic test, anthropometric measurements, counter-movement jump test with arms and yo-yo intermittent recovery test were performed. Signifi cant diff erences (p<0.05) were found in the professionals compared to U-20 and U-17 for body mass, height, body fat, VO 2max and for U-17 in relation to professionals in the isokinetic test. Signifi cant diff erences were also found between play positions (p<0.05) for body mass, height, VO 2max and isokinetic. Soccer athletes playing in diff erent positions have diff erent profi les of physiological characteristics and U-17 have a lower level of strength compared to professionals, suggesting the importance of training specifi city.

The purpose of this investigation was to examine the effects of a periodized strength training program and the use of infrared thermography (IRT) in injuries mapping in under 20-year-old (U-20) soccer players. In this study, 26 professional soccer players participated in strength training (ST) twice a week and were tested with IRT consistently across the 1-year. Strength, vertical jump, heat differences and injuries were tracked and analyzed. Results: 69 injuries occurred during 12 months of tracking; most identified injuries were: contusions, sprains, strains to the thigh (n = 16), ankle (n = 15) and knee (n = 12). Differences (>7 °C) in IRT patterns were noted among injured and non-injured athletes. Significant improvements in strength (p < 0.005) were found for vertical jump, bench press, front lat pull down, shoulder press, leg press, leg curl and squat. Number of injuries decreased from 23 (33.3%) to 14 (20.3%) when early year rates were compared to late year (p < 0.005). Combined ST and IRT represent useful strategies for reducing injuries among U-20 soccer players.

OBJECTIVE: To investigate the acute effect of static stretching on heart rate variability in trained men. METHODS: Eight subjects were randomly submitted to two situations, as follows: a static stretch protocol and 20 minutes at rest. The stretch protocol consisted of two sets of 30 seconds of static stretch of the chest muscles with a 40 second of interval between them. After 48 hours, the procedures were reversed so that all the subjects should were submitted to the two situations. The values of heart rate variability were measured before and after the experimental and control situation (stretch vs. rest). We registered the following cardiac variables: root mean square of standard deviation (rMSSD), the number of pairs of successive beats that differ by more than 50 ms (pNN50), low frequency (LF) and high frequency (HF). The Shapiro-Wilk and the paired Student's test were used for statistical analysis; a critical level of significance of p < 0.05 was adopted. RESULTS: No significant differences (p > 0.05) were found (stretching vs. control) to the RMSSD, pNN50, LF and HF indices. However, although no statistical differences were observed, the figures show large changes on mean values, suggesting an unclear effect on the sympathetic-vagal modulation. CONCLUSION: The present results suggest that a low intensity (motion range until discomfort point) and volume (1 minute) of static stretching does not significantly affect the acute sympathetic-vagal control in trained men. Because the protocol did not show differences regarding the studied variables, we suggest that there is not a sufficient level of physiological basis to perform this type of exercise in a traditional pre-exercise setting, if the purpose is obtain gains in physical performance.

Purpose. to compare isokinetic knee flexors and extensors concentric muscle strength in young soccer players of different ages and playing positions. Methods. Seventy-seven young male soccer players were divided into 3 age categories: U-15, U-17, and U-20, with the consideration of 4 game positions: goalkeepers, defenders, midfielders, and forwards. the concentric tests of the hamstrings (Hcon) and quadriceps (Qcon) were performed at 30°/s, 60°/s, and 180°/s, and the ratio of 180°/30° was calculated. Results. the values of Qcon for the U-15 turned out significantly lower in comparison with the U-20 in 30°/s and 180°/s and in the 180°/30° ratio. the Hcon values for the U-15 were significantly lower than for the U-20 at 30°/s, 60°/s, 180°/s, as well as in the 180°/30° ratio. Strength levels were shown to be significantly different between the 3 analysed categories. the goalkeepers presented with Qcon and Hcon values significantly higher than the other playing positions, regardless of the angular velocity used. Conclusions. U-15, U-17, and U-20 athletes do not have the same level of strength. the goalkeepers demonstrated high strength values, suggesting the importance of specific training for each game position.