Differences in the kinetics and kinematics of supported and un-supported landings of the rugby union lineout

Abstract

The aim of the current investigation was to comparatively examine the kinetics and kinematics of supported and un-supported landings during the rugby union line out. Eleven male line-out jumpers were tested under two conditions, ‘supported’ in which the lifters maintained supportive contact with the jumper until the jumpers’ feet touched the floor and ‘un-supported’ in which the lifters released the jumper once they had caught the ball. Kinematics were examined using an eight camera motion capture system and kinetics using a force platform. Differences between conditions were examined using paired t-tests. The findings showed the instantaneous loading rate (supported = 212.9 ± 102.5 BW/s & un-supported = 449.0 ± 142.4 BW/s) and vertical velocity (supported = 2.7 ± 0.4 m/s & un-supported = 4.0 ± 0.4 m/s) at foot contact were significantly larger in the un-supported condition. The findings from the current investigation indicate that if the line-out jumper is un-supported by the lifters in returning to the ground then their risk from injury is likely to be greater. Therefore, given the number of line-outs that are conducted per game it is recommended that this law be clarified to also specify supported lowering of the jumper at all levels of play.