As long as you are accelerating the load, momentum is not taking over. This is especially evident with cables because the implement you are using does not have the potential energy that the stack of weights does and you are not acting directlly on the stack. Anyhow, that's all semantics whatï¿½??s really happening when you accelerate a load quickly is you are calling the higher threshold motor units in to move a load lighter than what they are designed for, or have been trained to do.
So if for instance, your max bench is 315 lbs. and you are throwing up 225 lbs. as fast as possible, you are recruiting the some of not all of the muscle fibers suited to lift 315 lbs. because of the speed. Explosive movements call on the body to use maximal force. This is not a bad way to train, but I'd recommend going heavier for explosive movements, you do not want it to be to light.
This is the kind of stuff Waterbury is trying to get through our thick skulls.
For maximum benefit, I'd actually keep the speed up, not so much that you are sloppy or flinging weight around, but as fast as you can in good form. If you are looking for the burn, do more reps. Having slow concentrics or eccentrics is not going to give you much benefit. As the set goes the weight will slow down as muscle fibers fatigue, so don't worry about that part; you'll get your slow reps in.