Oops, watch the lazy trail leg on the left. The sequence on the right was taken one year before the sequence on the left. The trail leg action has become much more smooth, sadly it lost lots of momentum. The trailleg action can not be over-exaggerated enough.
The leadleg tilts the pelvis backwards just after take-off where it should go forward. The backward tilted pelvis prevents the trailleg being pulled through right. After that the athlete fails to reposition the pelvis before landing, leading to a high impact, breaking and poor take-off after the hurdle.