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Recently the following dilemma has been posed on another site that I frequent:
How come we preach to perform depth jumps for maximal height as opposed to the more common way of minimizing ground contact time (GCT)?
Here was my reply:
Shorter ground contacts are better at improving “reactive ability”. If you read Verkhoshansky’s work you will discover that he recommends DJ off a small box to improve RA. The smaller box correlates with shorter GCT. The aim though is still a maximal vert cause the goal is alwsys to improve maximal ability. Verk recommends DJ off of high boxes for explosive strength.
So there you have it. I like this way because it simplifies things.
1. how do you measure your GCT
2. since minimizing GCT requires submaximal effort how would you regulate volumes (areg) as you wont be able to know when performance decreases because measuring subsequent jump height will be inaccurate because you could compensate and keep height the same by increasing GCT and most people here cannot measure GCT. Of course we can assign arbitrary volumes but we know that is not optimal.
3. How do you know when your minimal GCT has turned into maximal force? .1 sec of a drop off is almost imperceptible. .05 is imperceptible. At this point you have lost the purpose of the movement.
4. How do you know if you have progressed? Can you tell if your GCT has decreased by 0.03 seconds?
So if you go off a lower box and still focus on maximal height you will train RA and be able to monitor performance more accurately
Also remember that DJ’s are a power exercise and as such power is a threshold best trained maximally. If you want RA at submaximal levels then perform low squat foot jumps and such.
So in summary do DJ of a low box for height if you want to develop RA. It trains the same thing and offers the same benefit as attempting to minimize GCT but with the added benefit of being easier to monitor progress and performance.
Perform DJ’s of a high box to increase explosive strength. They are two distinct exercises with different aims.
-Alex