Using weight training loads to get stronger, let's say if an athlete can produce let’s say 3-4x their BW (body weight) in force, but they cannot move it FAST, they lack IMPULSE.
We need to Get Stronger to produce more force for sprinting and jumping, but if we don't move that force fast, we are toast!
Less speed around the court.
Less inches on our jumps.
Even getting up to our best vertical takes longer.
Anytime you practice Sprints and different Jumping drills, aim for FAST aggressive outputs.
You should also have the intention of moving weight FASTER (of course with greater technique and control) through different % of loads.
This is also why Coaches exhausting athletes with "Boot Camp" style intensity while doing sprints and jumping drills DOES NOT make them move better for Volleyball! And honestly teaches them poor output in these movements.
Yes, the heart rate among other things will be conditioned to go further, but if speed and vertical is your focus, and in this sport it better be, it hurts those traits if you are often exhausted.