Does the new rugby union scrum sequence positively influence the hooker's in situ spinal kinematics?

Abstract

Background: Scrummaging is unique to rugby union and involves 2 ‘packs’ of 8 players competing to regain ball possession. Intending to serve as a quick and safe method to restart the game, injury prevalence during scrummaging necessitates further evaluation of this environment. Aims: The aim of this study was to determine the effect of scrummage engagement sequences on spinal kinematics of the hooker. The conditions investigated were: (1) live competitive scrummaging using the new ‘crouch, bind, set’ sequence; (2) live competitive scrummaging using the old ‘crouch touch pause engage’ sequence and (3) training scrummaging using a scrum machine. Methods: Inertial sensors provided three-dimensional kinematic data across 5 spinal regions. Participants (n=29) were adult, male community club and university-level hookers. Results: Engagement sequence had no effect on resultant kinematics of any spinal region. Machine scrummaging resulted in lesser magnitudes of motion in the upper spinal regions. Around two-thirds of the total available cervical motion was utilised during live scrummaging. Conclusions: This study indicates that the most recent laws do not influence the spinal kinematics of the hooker during live scrummaging; however, there may be other benefits from these law changes that fall outside the scope of this investigation.