Stretch and sprint training reduces stretch-induced sprint performance deficits in 13- to 15-year-old youth.

The recently reported static stretching impairments found in adults have not been studied in youth. Furthermore, stretch-training effects on sprint performance are equivocal, hence the purpose of this study was to examine the effect of stretch and sprint training on the acute effects of static stretching in 13-15 year olds. A total of 48 students were randomly divided into a sprint only and a stretch and sprint training groups who performed static stretching at the beginning and middle of the speed training sessions (6 weeks). Flexibility tests and 30-m sprints were performed before and after training. Sprint performance was evaluated with and without prior stretching. A main effect indicated that prior static stretching impairs sprint times at 10 (P = 0.01) and 30 m (P = 0.0005). Both groups improved times over 10 (0.7%; P = 0.04) and 30-m (1.5%; P = 0.0007) sprint distance after training. Stretch and sprint trained participants were more resistant to stretch-induced sprint deficits with 3.2% (P < 0.0001), 3.6% (P = 0.0002) and 1.3% (P < 0.0001) faster times at 5, 10, and 30 m, respectively, than the sprint only group. In conclusion, a stretch and sprint training program in 13-15 year olds diminished the detrimental effects of static stretching compared to a sprint only training program.

Appropriate interpretation of aerobic capacity: allometric scaling in adult and young soccer players.

OBJECTIVE: To compare aerobic capacity of young and adult elite soccer players using appropriate scaling procedures. METHODS: Twenty four male adult (mean (SD) age 24 (2) years, weight 75.7 (7.2) kg, VO2max 66.6 (5.2) ml/lbm/min, where lbm is lean body mass in kg) and 21 youth (14 (0.4) years, 60.2 (7.3) kg, 66.5 (5.9) ml/lbm/min) elite soccer players took part in the study. Allometric equations were used to determine the relation between maximal and submaximal oxygen cost of running (running economy) and body mass. RESULTS: Maximal and submaximal oxygen uptake increased in proportion to body mass raised to the power of 0.72 (0.04) and 0.60 (0.06) respectively. The VO2max of adult players was similar to that of the youth players when expressed in direct proportion to body mass--that is, ml/kg/min--but 5% higher (p<0.05) when expressed using appropriate procedures for scaling. Conversely, compared with seniors, youth players had 13% higher (p<0.001) energy cost of running--that is, poorer running economy--when expressed as ml/kg/min but not when expressed according to the scaling procedures. CONCLUSIONS: Compared with the youth soccer players, VO2max in the seniors was underestimated and running economy overestimated when expressed traditionally as ml/lbm/min. The study clearly shows the pitfalls in previous studies when aerobic capacity was evaluated in subjects with different body mass. It further shows that the use of scaling procedures can affect the evaluation of, and the resultant training programme to improve, aerobic capacity.

Endurance training and testing with the ball in young elite soccer players.

BACKGROUND: The aerobic capacity of soccer players substantially influences their technical performance and tactical choices. Thus, the assessment of soccer players' aerobic performance should be of interest for soccer coaches in order to evaluate and improve their endurance training sessions. In this study, we present a new test to assess aerobic performance in soccer by means of a specific dribbling track: the Hoff test. We further determined whether improvement in maximal oxygen uptake was reflected in increased distance covered in the Hoff test. METHODS: We tested 18 male soccer players (14 years old) both in the laboratory and using the Hoff test before and after 8 weeks of soccer training. RESULTS: The distance covered in the Hoff test correlated significantly with maximum oxygen uptake, and improved by 9.6% during the 8 week training period, while maximum oxygen uptake and running economy improved by 12 and 10%, respectively. Backward multiple regression showed maximum oxygen uptake to be the main explanatory variable for the distance covered in the Hoff test. CONCLUSION: The present study demonstrated a significant correlation between laboratory testing of VO(2max) and performance in the Hoff test. Furthermore, training induced improvements in VO(2max) were reflected in improved performance in the Hoff test. We suggest that it should be a goal for active U-15 soccer players to cover more than 2100 metres in the Hoff test, as this requires a VO(2max) of above 200 ml/kg(0.75)/min, which should serve as a minimum in modern soccer.