Ask any gymnast or coach 'when does heel drive start on vault?' and the majority would say from the springboard to the vault table. In other words, once the feet contact the springboard the heels are driven upwards over the center of mass to facilitate rotation. I would challenge this answer in that I believe heel drive should start before the feet contact the springboard, during the hurdle phase. This process is very quick, allows for explosive compression of the springboard, which in turn will facilitate a stronger heel drive in the end. Any thoughts or disagreements?