Biomechanics of the running drop punt kick with respect to the development of quadriceps strains

Quadriceps strains affect the muscles at the front of the thigh, particularly rectus femoris. They are one of the most common injury types in the AFL, extracting a heavy toll on a club's injury list. Video evidence suggests that rectus femoris strains may often occur due to under-striding when trying to slow down in running. Under-striding when 'slowing down' the kicking leg during the final step of the running drop punt kick in Australian football is the likely 'cause' of quadriceps strains. The deceleration component of the final step of the kicking leg before ball contact is very similar to the mechanics observed in a deceleration movement in which a quadriceps strain can occur whilst running. It is therefore highly probable that deceleration movements, whether occurring during running or a running kick, are more likely to result in a quadriceps strain compared to other movements. This combination of under-striding when trying to slow down causes the body to lean backwards and the leg to move farther behind the body than normal, which places extra stress and strain on the rectus femoris. It is not established whether strain injury actually occurs during the back-swing phase (when the muscle is at greater length) or the ground contact phase (when there is greater stress on the muscle from external forces), but it is considered unlikely that quadriceps strains regularly occur during ball contact. Wet weather conditions (ie, heavier balls) are not be a risk factor, nor is ball inflation pressure. Quadriceps fatigue, weakness or dysfunction may contribute to an under-stride (by failing to progress the leg fully during the preceding swing phase) and therefore these factors may also be risks for quadriceps strain injury. (author abstract)