Time very slow in rendering animation

hi,
I have an animation with 3d studio max 2013 , I noticed that if imposed SOLID ROCK with key Animation FUll , time to render one frame increases significantly , with respect to time to render a single frame , where am I wrong? someone has already encountered this problem ?
thanks to all ,

same problem here, I can render single frame in no time but when I try to render animation thru fly through animation time increases slowly slowly

As a test, try eliminating all animation from all lights.