Participation of the agonist and antagonist knee extensor muscles in drop kick, placing kick and up and under kick, in rugby athletes

Abstract

Introduction: Rugby is a sport that implies constant physical contact, therefore it represents a high rate of injury risk, considering that the hip injury represents an average of 109 days without training per season [1]. The quadriceps femoris of the shooting lower limb is the muscle with the highest injury rate, being the exact moment of impact with the ball the main mechanism [2]. The point of this study is to verify the muscular participation in the exact moment of impact, in the three different types of kick, in order to allow the development of a prevention program for muscular injury in a rugby player.

Methods: Twelve male rugby players, from Sport Lisboa e Benfica, with mean age 21.7 ± 2.7 years were selected. These athletes were able or allowed to shoot and had no kind of pain. Firstly, the athletes made a quick warm up exercise, and then, they performed the three types of kick. Electromyography analysis was used in the data collection. The chosen method was muscular activation, and the electrodes were placed in the rectus femoris and biceps femoris muscles [3]. The electromyography data had been synchronized with the tri-axes motion acceleration sensor (obtained through the Bioplux software) in order to identify the exact moment of impact between the foot and the ball. In addiction a video recording has been made to identify the beginning of the movement and the type of kick. The study was approved by Sport Lisboa e Benfica and all participants gave their informed consent

Results: Through data analysis, it was possible to identify a previous muscular activation which decelerate the movements, on this case the biceps femoris, which presents a higher percentage of activation than the rectus femoris. On the drop kick, the biceps femoris is the one that activates immediately before ball impact, exactly the same that in the up and under kick and on the placed kick. On the placed kick, there's a previous preactivation of the biceps femoris.

Conclusion: The study is still preliminary. It was possible to identify a triphasic pattern on the ballistic gestures made by the players, as described on the literature. Further studies, with larger samples are needed. Comparing athletes with different field positions should be interesting since different gestures implies different muscle recruitments with eventual distinct injuries.