Initially all pole vault drills are done with a straight pole because we need to learn to move the pole forwards and swing on a straight pole before bending. This is a straight pole inversion drill that gets the vaulters used to being upside down on the pole whilst jumping.
We are looking to hit the same take off position as all the previous drills and kick the left leg through into inversion, using its momentum to help rock back and invert upside down on the pole. This is the reason we keep the left leg back at take off so there is increased swing on the leg as it comes forwards, using it as a pendulum. Fast right arm, kick, swing and invert.