This is accomplished by the elbow leading the ball... when throwing a change up, she simply eliminates the whip by ensuring the ball is leading the bent elbow in a shoving fashion. This is the most basic way to describing it...
I am trying to figure out if my DD has enough range in her pitch speeds or if we need to work on a more significant off speed too. My DD's cruising speeds for RB is about 50-52, FB is about 52-53, her DB is usually 54-55 (I think that may be coming up a bit more now) and CU is about 48. Hoping with some posture work and work on keeping spins true this fall and winter that there may become more of a spread. Such as when she focuses on true spin for her RB it is slower than if she gets lazy and it goes bullet and then it's same speed as FB just with upward trajectory. And working on good 12-6 spin on DB instead of tilted seems to keep that on the upper end of speed.
But I'm wondering if to fool batters if we need to have two speeds for the same pitch like Sluggers is explaining . . .
I think the change up would be more effective if it were slower. Usually look to 9-12 MPH slower than FB.