Impact Of Competitive Level And Age On The Strength And Asymmetry Of Young Soccer Players

Introduction: Muscular strength is an essential capacity for soccer players; however, the profile of this capacity has not yet been clearly established in young players. Objective:To compare muscular strength performance in the countermovement jump (CMJ) task and the presence of lower limb asymmetry among soccer athletes of the under 15 (U15), under 17 (U17) and under 20 (U20) categories, and between two teams of different competitive levels. Methods: One hundred and fifty one young soccer players of three different categories (U15, U17 and U20) from two teams in the Brazilian first and second divisions performed six vertical jumps in a system of two force plates. Ground reaction force (GRF) was used to calculate jump height and to obtain the variables Peak force (F-MAX), Impulse (I) and Peak power (P-MAX) with regard to body mass and the respective asymmetry values. Results: No differences were found in the performance and asymmetry variable between the categories (Jump height: p=0.23; F-MAX: p=0.15; I: p=0.1 1; P-MAX: p=0.32; F(MAX )asymmetry: p=0.21; I asymmetry: p=0.58; P-MAX asymmetry: p=0.58). The first division club had higher muscle strength and asymmetry values than the second division club (Jump height: p<0.01; I: p<0.01; P-MAX: p<0.01; F-MAX asymmetry: p<0.01;I asymmetry: p<0.01; P(MAX )asymmetry: p<0.01), except for F-MAX (p=0.63). No variable had an interaction effect (club x category). Conclusion: As categories progress, jump height, relative I, P-MAX and F-MAX values and their respective asymmetries are stable. The asymmetry and strength performance of the first division club were higher than that of the second division club, except for F-MAX, indicating that the competitive level may influence strength performance and the development of asymmetry.