Speed Killls what you don't understand is that there is a cost effectiveness doing exercises. The closer to running specific the better but there is also a time cost vs. injury. Just because something has a different energy system doesen't mean you should be doing these exercises all day. Plyometrics do great things but if an athlete already has great elasticity and coordination then they might help a little but the injury cost after lots of endurance training they are dangerous. You are certainly a sprint coach. Runners should have just one coach because everything affects the body and the mind.
Even if you are explosive you have to keep working on this.
If you do not use it, you lose it. There is no such thing as "natural" talent in maintaining 46 second 400 speed. You must always work on it, even if only in maintanence mode.