As we go through the movements of T'ai Chi, or should that be the other way around, there is no break or discontinuity.
Cheng Man Ch'ing describes this as movement and swing, swing and movement. We turn the waist and the hands follow. When the waist stops moving, so do the hands. However, the energy produced by the initial waist turn after it stops produces the next movement as there is a "swing" derived from it. And so it continues, on and on.
This key principle is what distinguishes the dross from the sublime. Otherwise we end up moving like a brick, a stiff.
Source: Cheng Man Ch'ing's Advanced Form Instructions by Douglas Wile, Sweet Ch'i Press, 1985. ISBN 0-912059-03-6