A laboratory protocol for shoulder-head and head-ground dummy head accelerations during player high-speed rugby tackles.

Background: The purpose of this study was to demonstrate the effectiveness of a novel laboratory testing protocol for dummy head biomechanics of the shoulder-head and subsequent head-ground impacts during rugby tackles. Currently, no research in tackles utilizes a real player as the tackler and considers the second impact when the opponent's head hits the ground. Methods: A dummy was instrumented with an inertial measurement unit (IMU; 1,200 Hz) behind the right ear. Eleven rugby players with a shoulder placed IMU executed right shoulder high tackles to the left side of the dummy's head at two closing velocities (high-speed 15-17 km/hr and very-high-speed 21-23 km/hr) for three dummy head conditions (no headgear, club-level headgear, professional-level headgear). Peak resultant linear and rotational accelerations were calculated for the first impact event (shoulder-head) for the player's shoulder IMU and for the two impact events (shoulder-head, head-ground) for the dummy head IMU. Results: Whilst the player experienced low linear accelerations (fast-speed = 10 g, very-fast-speed = 13 g) through their shoulder during the tackle impact (shoulder-head collision), the linear accelerations were six times higher (63 g; Conclusions: This study demonstrates the effectiveness of a protocol measuring linear and rotational accelerations of a dummy's head during high-speed rugby tackles where a real player's shoulder hit the dummy's head and the dummy's head hit the floor. Trialing the protocol showed high impact accelerations experienced when receiving a tackle did not reduce with headgear. The experimental methodology and tools developed provide the basis for more complete testing of head biomechanics in tackles.