Determinant factors of repeat sprint sequences in young soccer players.

The aim of this study was to investigate the relationships between repeated explosive effort sequences (20+20 m shuttle sprint with change of direction, kicking and jumping), metabolic response (lactate and ammonia), and fitness qualities (strength and endurance) in under-19 soccer players. 21 players completed: 1) sprint test: 30 m (T30) and 40 m (20+20 m) shuttle sprints; 2) countermovement jumps (CMJ); 3) maximal kicking; and 4) 9 repeated-explosive effort sequences (RES); 4) a progressive isoinertial loading test in full squat to determine the load which subjects achieved ~1 m · s(-1) (V1-load); 6) Yo-Yo Intermittent Recovery Test Level 1 (YYIRT-1). Mean sprint time of the 9 repeated sprints (RSA(mean1-9)) showed correlation with V1-load (r=- 0.52 [- 0.79, - 0.25]) metabolic response (lactate, r=0.67 [0.47, 0.87] and ammonia, r=0.53 [0.27, 0.79]). YYIRT-1 correlated with RSA(mean1-9) (r(w)=- 0.78 [- 0.92, - 0.64]) when the body weight was controlled. Furthermore, the 3 first sprints (RSA(mean1-3)) correlated with RSA(best) (r=0.93 [0.88, 0.98]), V1-load (r=- 0.64 [-0.86, - 0.42]), and T30 (r=0.63 [0.41, 0.85]). These results suggest that the soccer player's lower body strength (V1-load, jumping and sprinting) explains a large part of the performance in the first sequences, whereas the aerobic capacity, estimated through YYIRT-1, becomes more important to performance as the number of sprints is increases.

Influence of the Numbers of Players in the Heart Rate Responses of Youth Soccer Players Within 2 vs. 2, 3 vs. 3 and 4 vs. 4 Small-sided Games.

The purpose of this study was to compare heart rate (HR) responses within and between small-sided games (SSG) training methods in elite young soccer players. Twenty-seven youth soccer players (age: 16.5 ± 0.5 years, height: 174.5 ± 5.5 cm, weight: 62.9 ± 8.3, velocity at maximal aerobic speed (MAS): 15.9 ± 0.9 km.h(-1)) performed 3 different SSG (2 vs. 2, 3 vs. 3, 4 vs. 4 without goalkeeper). In each SSG, HR was continuously measured and expressed as a mean percentage of HR reserve (%HRreserve). The mean %HRreserve calculated during the SSG was significantly lower during 4 vs. 4 (70.6 ± 5.9 %) compared to 2 vs. 2 (80.1 ± 3.6 %, p<0.001) and 3 vs. 3 (81.5 ± 4.3 %, p<0.001) SSG. Regardless of the time spent above 60, 65, 70, 75, 80, 85 and 90 % of HRreserve, 4 vs. 4 solicited lower percentage of time than 3 vs. 3 and 2 vs. 2. Intersubject coefficients of variation were significantly higher during 4 vs. 4 compared to 2 vs.2 and 3 vs. 3. The %HRreserve after 30s of recovery was significantly higher for 3 vs. 3 (70.6 ± 5.3 %) compared to 2 vs. 2 (65.2 ± 4.8 %, p<0.05) and 4 vs. 4 (61.6 ± 9.3 %, p<0.05). In conclusion, this study demonstrates that the physiological demands is higher during 2 vs. 2 and 3 vs. 3 compared to 4 vs. 4 in youth soccer players. This difference could be due to that young soccer players do not have the same technical ability and experience as adult players and thus, their activity during the 2 vs. 2 and 3 vs. 3 induces a greater physical demand due to their lack of experience. The age of the players could be linked with the physical demands within small-sided games.