Effects of three different training programmes on instep kick in preadolescent football players

Introduction The Instep Kick (IK) is a basic element of a soccer game. It is a multi-joint activity affected by numerous factors, such as strength and power of the muscles involved in the kick (2), movement timing and stretch-shortening cycle among segments that contribute in the kick (3), and approach of the player to the ball (3). The purpose of this study was to investigate the effects of specific (instep kick), non-specific (i.e., small side game and condition training) training on the speed of the ball in an IK on dominant and non-dominant legs in preadolescent Italian football players. Methods Eighteen male football players (age: 11 y, height: 1.45±0.09 m, weight: 36.9±6.0 kg) were recruited from an amateur Italian football team. Participants followed 6-weeks of specific training, in addition of their baseline football training and were randomly divided into three groups: 1) Instep Kick Group (IKG, n=6); 2) Conditional Group (CG, n=6) and 3) Small Side Games Group (SSG, n=6). In all the training sessions (twice per week), IKG performed 20 IK (using maximum force) into the goal with dominant and non-dominant legs; CG performed four different conditional football exercises (i.e., 10 sets of the T-drill, 10 sets of 4 consecutives alternate bipodalic lateral jumps, 8 series of 5 consecutive bipodalic frontal jumps, 10 series of the stop-and-start drill); and SSG performed 20 minutes of 3 vs 3 small side game. The football players were tested pre and post training periods on the speed of the ball in an IK on dominant and non-dominant legs. In each day test, participants performed four kicks with the left and the right leg and the speed of the ball was recorded using a speed radar gun (model#10-1925, Bushnell Outdoor Products, Overland Park, KS, USA). Among the 4 kicks, the higher speed recorded was used in the statistical analysis. Two-way analysis of variance with repeated measures on one factor was used in order to detect differences among the three groups and between pre and post training period, in the dominant and non-dominant legs separately. Least Significant Difference test (LSD) was used as post-hoc analysis. Results Significant improvement in IK of about 5.7% was found in each group between pre and post training periods in dominant leg (Within-subjects difference: F(1,15)=21.805, p<0.001). Significant interaction was found in non-dominant leg (Interaction: F(2,15)=21.805, p=0.001). The LSD post-hoc test showed statistical improvement only in IKG of 10.3% between pre and post training period (p=0.002). Conclusion The three different trainings produced the same improvement on the speed of the ball in an IK on dominant leg. Conversely, on non-dominant leg it was found different effects between training methods. In particular, the IKG obtained larger improvement than the CG and SSG on non-dominant leg. The young football players often use the dominant leg to manipulate the ball (1), and for this reasons the dominant leg did not require any specific training to improve the speed of the ball in an IK. For the same reason, the 11 years old football players obtained larger improvement on non-dominant leg, probably because trained to repeat the IK numerous times. References 1. Bjelica D, Popovic S, Petkovic J. Comparison of instep kicking between preferred and non-preferred leg in young football players. Monten J Sports Sci Med 2013; 2: 5-10 2. Dörge HC, Andersen T B, Sørensen H, Simonsen EB, Aagaard H, Dyhre-Poulsen P, Klausen K. EMG activity of the iliopsoas muscle and leg kinetics during the soccer place kick. Scand J Med Sci Sports 1999; 9: 195-200 3. Kapidžić A, Huremović T, Biberovic A. Kinematic analysis of the instep kick in youth soccer players. J Hum Kinet 2014; 42: 81-9