THE CURVE EDITOR

You would utilize the curve editor to polish your animations. You may use the animation's function curve to change the timing.

You may also access the curve editor from the graph editor menu at the top of 3ds max.

Ensure that on the Auto Expand and Auto Select that animated is checked. This will also select any custom properties you have made. The curve that is green that you see here is the function curve which is how your rig moves about from key frame to key frame. You may alter the movement of the rig from here.