Players work in pairs and stand across the court from each other. One player starts with the ball and overhand passes the ball high in the air to their teammate.
The teammate then sets the ball in the air above their head, digs it on the way down, and then sets the ball back to their teammate who does the same thing.
During this exercise, the players must adapt from being in a position to set to being in an underhand body position, and this can be done easily with correct footwork. Players must be able to adjust quickly with their arms to go from setting to digging quickly.
When passing underhand, ensure the player looks forward to take a look at their teammate's position.
New hitters rarely miss because of their arm. They miss because of their feet. Build a reliable approach, then time it with your setter.
When your hitter gets stuffed, five teammates standing and watching is how you lose the point. Good attack coverage turns a blocked ball into a second swing.
Coaches spend hours correcting arms in serve receive when the real fault is almost always the feet. Fix the movement and the platform fixes itself.