Author(s): NAKAMURA, H., YAMASHITA, D., NISHIUMI, D., NAKAICHI, N., HIROSE, N., Institution: WASEDA UNIVERSITY: WASEDA DAIGAKU, Country: JAPAN, Abstract-ID: 1481

INTRODUCTION:
Change of direction (COD) ability is considered a critical motor ability in football, with recognized potential for improvement across various adolescent age groups. Previous studies have shown the effectiveness of eccentric training and COD modification training in enhancing COD performance among adults. However, information on the efficacy of these training methods in adolescents remains limited. This study aimed to compare the effects of different training methods on COD performance and kinematics among adolescent male football players.
METHODS:
Fifty-eight junior high school male football players participated in this study and they were divided into three groups: Control group (CON group) consisted of 16 players who adhered to regular soccer training only. In addition to the regular soccer training, 21 players underwent COD modification training, which included drills at various angles and distances (COD group); another 21 players engaged in strength and plyometric training with an emphasis on the eccentric phase of movement (SP group). The seven-week intervention consisted of 12 sessions, each lasting approximately 15 minutes and held once or twice weekly. Participants underwent three trials of the Pro-Agility test and two trials of the 20 m sprint test before and after the intervention.
Total time was measured using timing gates for both the Pro-Agility and 20 m sprint tests, with the COD deficit (CODD) determined by the difference between these results. 3D kinematic data from the Pro-Agility test were obtained using a markerless motion capture system, facilitating the calculation of the center of mass (COM) velocity and kinematics for the trunk and lower limbs. The test consisted of 5 m, 10 m, and 5 m segments, each divided into acceleration (Acc) and deceleration (Dec) phases based on COM velocity, and further divided into early and late halves. The mean acceleration of the COM for each phase was computed. A two-way mixed ANOVA, incorporating both group and time as factors, was conducted, with Bonferroni-corrected pairwise comparisons applied for detailed analysis when significant interaction effects were noted.
RESULTS:
Significant interactions were observed for CODD, 2nd Late Dec, 2nd Early Acc, and trunk lateral lean angle at 2nd turned foot contact. CODD was significantly improved in the COD group (p=0.027). 2nd Late Dec was significantly increased in the COD and the SP group (p=0.012 and 0.006, respectively). 2nd Early Acc was significantly decreased in the SP group (p=0.002). Trunk lateral lean angle at 2nd turned foot contact were significantly increased in the COD group (p= 0.004).
CONCLUSION:
In adolescent male football players, seven weeks of strength and plyometric training improved deceleration ability in the COD task. However, it did not lead to improving COD ability. On the other hand, seven weeks of COD modification training improved deceleration ability and trunk kinematics in COD task and it led to improving COD ability.