Players run along the sideline as far as the attack line where they performs squat-jumps followed by three quick jumps. The drill starts and ends with runs that involve arm swinging.
Have players jump with arms extended as high as they are prepared to block.
This exercise allows players to develop explosive power of lower limbs and shorten reaction time when blocking which is very important for blockers.
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.