IN-SEASON INTEGRATIVE NEUROMUSCULAR STRENGTH TRAINING IMPROVES PERFORMANCE OF EARLY- ADOLESCENT SOCCER ATHLETES CHARALAMPOS PANAGOULIS, 1 ATHANASIOS CHATZINIKOLAOU, 1 ALEXANDRA AVLONITI, 1 DIAMANDA LEONTSINI, 1 CHARIKLIA K. DELI, 2 DIMITRIOS DRAGANIDIS, 2 THEODOROS STAMPOULIS, 1 TRIANTAFYLLOS OIKONOMOU, 2 KONSTANTINOS PAPANIKOLAOU, 2 LEFTERIS RAFAILAKIS, 1 ANTONIOS KAMBAS, 1 ATHANASIOS Z. JAMURTAS, 2 AND IOANNIS G. FATOUROS 2 1 Department of Physical Education and Sport Sciences, Democritus University of Thrace, Komotini, Greece; and 2 Department of Physical Education and Sport Sciences, University of Thessaly, Trikala, Greece ABSTRACT Panagoulis, C, Chatzinikolaou, A, Avloniti, A, Leontsini, D, Deli, CK, Draganidis, D, Stampoulis, T, Oikonomou, T, Papaniko- laou, K, Rafailakis, L, Kambas, A, Jamurtas, AZ, and Fatouros, IG. In-season integrative neuromuscular strength training improves performance of early-adolescent soccer athletes. J Strength Cond Res XX(X): 000–000, 2018—Although forms of integrative neuromuscular training (INT) are used extensively for injury prevention and treatment, no information exists about its effects on performance of adolescent athletes. We investigated the effects of an in-season INT intervention on performance of early-adolescent players using a 2-group, repeated-measures design. Twenty-eight early adolescents were randomly assigned to a control group (CG, participated only in soccer training, N = 14, 11.4 6 0.57 years, Tanner stage 2.8 6 0.6) or an experimental group (INT was added to conventional soccer training, N = 14, 11.2 6 0.5 years, Tanner stage 2.6 6 0.5). Integrative neuromuscular training (8 weeks, 3 sessions$wk 21 ) aimed to develop core strength, hamstrings eccentric strength, hip/knee musculature, and dynamic stability using body mass exercises, medicine balls, rocker boards, Bosu, stability balls, etc. Ball shooting speed, speed (10, 20-m), change of direction (COD), jumping perfor- mance, and strength were measured before and after training. A 2-way repeated-measures ANOVA was used to analyze data. Integrative neuromuscular training improved 10- and 20-m speed (2.52–2.13 and 3.61–3.39 seconds, respectively, p , 0.05), strength (40.1–44.4 kg, p , 0.05), jumping ability (squat jump: 16.3–17.9 cm; countermovement jump: 19.1– 20.3 cm, p , 0.05), COD (18.0–17.3 seconds, p , 0.05), and shooting speed (73.8–79.0 km$h 21 , p , 0.05). In the CG, soccer training caused an improvement of smaller magnitude in 10 m and shooting speed (p , 0.05), whereas COD and jumping performance remained unaffected while 20-m speed, COD, and strength deteriorated. These results indicate that an 8-week INT program may induce positive adaptations in per- formance of early-adolescent soccer players during in-season training, suggesting that INT may be an effective training inter- vention for this age group. KEY WORDS functional training, adolescence, in-season training, agility INTRODUCTION Y outh soccer incorporates actions requiring the generation of high and rapid force output in con- centric and eccentric fashion such as sprinting, accelerations and decelerations, jumping, change of directions (COD), lateral motion, and powerful skill–based motions such as shooting, tackling, and dribbling (5,42). In general, matches and practice sessions in youth soccer are characterized by shorter durations (60–80 minutes) com- pared to adults with players covering 4.5–8.1 km at an intensity that approximates 69–91% of their maximal heart rate (5,42). It has been shown that almost 3% of total dis- tance covered by young players during a game is sprinting (5). In fact, the most critical actions during a match (scoring, defense, and ball possessions) are those taking place using sprinting and may affect the final result of a match (43). Numerous studies have examined the effect of plyometric, strength, and neuromuscular training on general and soccer- specific performance in youth (7,8,19,25,32,46,47). Pro- longed participation in strength training programs seems to induce large gains in strength and moderate improve- ments in speed and other factors related to soccer performance (7,8,25,47). Furthermore, implementation of well-structured Address correspondence to Ioannis G. Fatouros, ifatouros@pe.uth.gr. 00(00)/1–11 Journal of Strength and Conditioning Research Ó 2018 National Strength and Conditioning Association VOLUME 00 | NUMBER 00 | MONTH 2018 | 1 Copyright ª 2018 National Strength and Conditioning Association