A review of the biomechanical determinants of rugby scrummaging performance

Abstract

Background:The scrum is a physical contest unique to the game of rugby union, important for determining match outcomes. Objective: This review will describe the current understanding of the kinetic and kinematic determinants of successful scrum performance to support coaching interventions and inform on future research. Methods: Literature review. Results: Individual and combined scrumming forces increase with playing level but there is no concurrent increase in body mass or player strength. There is very little variation in individual kinematics between individuals and across levels of play, suggesting that there are limited possible techniques for successful scrummaging. Live scrum contests are dynamic and require constant adjustments to body positions in response to increased compressive force and exaggerated lateral and vertical force components. Skilled performers are able to exert high levels of horizontal force while maintaining effective body positions within this dynamic environment. Conclusion: Success in scrummaging depends on the optimisation of joint angles and force production at the individual level, and the coordination of effort at a team level. The analysis presented here demonstrates that producing large scrum-specific forces and achieving the optimal 'body shape' are essential for successful scrum performance.

Calibration and Multiple Reliability Assessments of a Scrum Machine Instrumented to Measure Force

“…The two opposing scrum packs then bind against each other and contest for possession of the ball, which is rolled into the space between the two scrum packs [1]. If one scrum pack can produce more force than the other scrum pack, it may be able to push the opposing scrum pack backward and away from the ball, thus gaining possession of the ball [2,3]. Thus, the scrum is a tactically important part of the game, because winning ball possession in the scrum determines which team possesses the ball and can make offensive progress toward scoring.…”

“…Following Preatoni and colleagues' research [4][5][6][7], World Rugby changed the laws (i.e., rules) of the sport to minimize scrum impact forces, with the goal of decreasing injury rates. As a consequence of the rule changes, the scrum tends to last longer (from only about 3 s on average to closer to 8 s) [2,3]. This provides more opportunity for scrum packs to contest for the ball; knowing the force development characteristics of their scrum pack could help coaches make tactical, training, and player-selection decisions on the basis of empirical data and experimentation.…”

“…This provides more opportunity for scrum packs to contest for the ball; knowing the force development characteristics of their scrum pack could help coaches make tactical, training, and player-selection decisions on the basis of empirical data and experimentation. Two recent systematic reviews both highlighted the lack of research about scrum performance and the need for more data about the forces generated in the scrum and the force-time curves associated with scrummaging, especially during the sustained push phase where players contest for the ball [2,3]. Currently, there are several tactical decisions made by coaches in the scrums, such as using tight or loose binds, whether to try to wheel (i.e., attempt to rotate the whole scrum), and how much the flankers or #8 player should push versus being loosely bound and ready to disengage to make the tackle or support the ball carrier; however, none of these tactical decisions is informed by data.…”

“…Reliability is a crucial component of any fitness test that indicates how well a test produces the same result under similar conditions [12]. While testing force production in a scrum machine is still rare, especially outside of research, and is in a nascent stage of research [2,3], we can look to similar strength tests for guidance. Pushing against a scrum machine for testing force production has been, in the prior literature and in the presented studies below, an isometric force production task [2,3].…”

“…While testing force production in a scrum machine is still rare, especially outside of research, and is in a nascent stage of research [2,3], we can look to similar strength tests for guidance. Pushing against a scrum machine for testing force production has been, in the prior literature and in the presented studies below, an isometric force production task [2,3]. Thus, the two previously used tests that are the most similar to testing are an isometric squat (highly biomechanically specific to a scrum) and, to a slightly lesser extent, the isometric midthigh pull [13][14][15].…”