John Dunning has seen a lot of volleyball players, and knows how to correct bad hitting form. One-foot landings make players injury-prone and is a common bad habit in outside hitters, especially when they tend to lean out to catch balls in the middle of their shoulder.
How Dunning fixes it: Angle your approach so your hand is centered on the ball. This might mean starting from a wider position so you don’t have to reach outside of the ball if it travels past your shoulder. Dunning would eliminate players from his practice if they repeatedly landed on one foot. This tactic forced players to pay attention to their approach and prevent injuries.