Vocal professionals, as well as people with vocal issues, must kick-start their vocal cords gradually, in order to make them move safely and comfortably during a vocal-effort.

In other words, they must accelerate their movement, so the vocal cords will start the performance when their cords are already on the move, not when they are at rest.

Vocal effort, just like any physical effort, is much easier when you build up a momentum. It is essential for guaranteeing a smooth, and effortless operation of the cords, especially when the performance required high vocal intensity.