​The AcuSpike Spike Trainer has a ruled height indicator and is infinitely adjustable with the bi-directional hand crank. Like a vertical jump tester, it will show you exactly how high each player is capable of jumping. Since each ball releases, you'll know if the player hit the top of the ball and the corresponding trajectory.
Keeping track of each player's vertical jump using the AcuSpike Spike Trainer is easy. With improvements in approaching technique, conditioning, and many repetitions, vertical jump will improve. Keep track of each player's max "hitting height" progress over time with the AcuSpike Spike Trainer's height indicator.