The easiest way to improve a vault is to increase horizontal speed on contact with the Board.
I like this 2015 article by Valentin Uzunov because it links to videos.
Sprint Training for Vault – Off-season Training Program for 7-12yr old Gymnasts
Click PLAY or watch a sample from Valentin’s TheGymPress YouTube channel.
Thanks Carla.
Gymnastics Coaching.com 