# Head impact forces in rugby tackles are influenced by tackler position and the ball carrier instantaneous speed at contact in front-on, one-on-one tackle scenarios

## TL;DR

This study finds that rugby tackle techniques and speeds affect head impact forces, suggesting safer tackling strategies.

## Contribution

The study identifies specific tackle techniques and speeds that influence head kinematics in rugby tackles.

## Key findings

- Ball carrier's speed at contact predicts head kinematics for both players.
- A flexed head-kyphotic posture increases tackler's head kinematics but reduces ball carrier's.
- Lowering body height increases head kinematics for both players.

## Abstract

It is not well understood how tackling technique influences the inertial head kinematics of a tackler or ball carrier. This study identified the modifiable components of the tackler's technique (including instantaneous speed at contact) that predicted inertial head kinematics of a male tackler and ball carrier during a front-on, one-on-one, ‘slow speed’ rugby tackle.

Three-dimensional motion capture recorded 455 torso tackles across 15 rugby players. Principal component analysis identified four significant tackle related variables: ‘flexed head-kyphotic posture’; ‘body height lowering strategy’; ‘instantaneous speed at contact—ball carrier’; ‘instantaneous speed at contact—tackler’.

The ball carrier's instantaneous speed at contact, not the tackler, predicts inertial head kinematics of the tackler's and ball carrier's inertial head kinematics (p ​< ​0.05). Tacklers that adopt a more ‘flexed head-kyphotic posture’ (i.e., they were looking downwards towards the ground, adopted a kyphotic posture), resulted in higher inertial head kinematics for the tackler but lower inertial head kinematics for the ball carrier (p ​< ​0.001). A tackler with a ‘body height lowering strategy’ resulted in higher inertial head kinematics for both players (p ​< ​0.001) by tilting their pelvis forward to primarily flex their hips, and adopting an upright trunk posture with a neutral lordotic posture.

To reduce the tackler's peak inertial head kinematics, the tackler could adopt a tackle strategy that looks upwards (i.e., not looking to the ground) and adopts partially bent-at-waist (i.e., is not upright) and avoids a kyphotic posture or tilting their pelvis forward to primarily flex their hips to lower their body height.

This is not a clinical trial.

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