Using markerless motion capture to explore changes in tackle kinematics and load-based tackling technique proficiency

The purpose of this study is to explore how PlayerLoad^TM and tackle kinematics change during a simulated tackle in relation to tackle technique proficiency. Twenty amateur male rugby union players performed 12 tackles on a tackle contact simulator while wearing a microtechnology device. Each tackle was video-recorded and analysed using tackler proficiency criteria. Based on the criteria tackles were split into three categories: lower (≤7 AU), medium (8 AU) and higher scoring tackles (≥9AU). Markerless motion capture was used to derive kinematic variables for each tackle. Kinematic data and PlayerLoad^TM variables were analysed between the three different categories. Power of the shoulder at contact in the higher scoring tackles (27.8 [95%Cl: 11.36-44.3]kW) was significantly higher than in the lower scoring tackles (7.9 [5.3-10.5]kW). Force of the shoulder at contact was higher in the lower technique scoring tackles (3.6 [2.6-4.5]kN) than in higher scoring tackles (-2.1 [-0.8-5.1]kN), but in the opposite direction to where the tackle is made. Technically proficient tackles are more powerful because players are applying their force correctly at the point of contact. Despite the higher technical proficiency group being more powerful, the external loads experienced by the player may be similar for all tackles.