Fast BB Shrugs (video inside)

[Kut_Man07]

Im just looking for POSITIVE advice on this workout. Is it really bad to do fast bb shrugs? It works good for me either way (slow, fast), but are they considered "wrong". The reason why I do it fast is for explosiveness, b/c I use my leg muscles for xtra movement:

Video: http://www.megavideo.com/?v=8R7BZODI

[WvrDuDe]

this doesnt build exposiveness, it builds tendon problems.
Explosiveness is when you PAUSE between reps, but the reps themselves fast.