Relationship between the ground reaction force and lower limb movement during experimental tackle motion in rugby football players of various play levels

BACKGROUND: The present study investigated effective tackle motions in rugby by analyzing the relationship between the running velocity (greater trochanter velocity [GTV]), lower limb movement, and ground reaction force (GRF) during tackle movement.METHODS: Targeting sixteen rugby players of various play levels, we recorded the tackle motion at 100 Hz using 7 infrared cameras. The GTV, lower limb joint angle, and angular velocity were calculated from the obtained three-dimensional coordinate values. Regarding the GTV, the impulse and peak value in the horizontal component, mediolateral component and vertical component of the stepping foot were calculated from the signals obtained from one force plate.RESULTS: A significant negative correlation (P<0.05) was found between the GTV when the foot was on the ground and the braking component of the GRF until it collided with the tackle bag. In contrast, there was a significant positive correlation between the GTV during the tackle bag collision and the flexion-extension angular velocity of the hip joint (P<0.05), knee joint (P<0.01), and ankle joint (P<0.05) during the tackle bag collision. Furthermore, there was a negative correlation between the GTV at the time of the tackle bag collision and the vertical, horizontal, and propulsive impulse component from tackle bag collision to the takeoff of the stepping foot (vertical impulse: P<0.01, horizontal impulse: P<0.01, propulsive impulse: P<0.001).CONCLUSIONS: The tackle movements of athletes with a high trochanter velocity indicated that they were aggressively kicking the ground by increasing the extension speed of the entire lower limb while applying a large brake when stepping, and there was no significant force applied to the ground after the tackle bag collision.