Watch today’s PGA Tour players; hardly anyone starts the club back slowly. The part of the swing that should be slow, is the transition from the backswing to the downswing. If the heave or initial move of the backswing is powerful, but brief, for the first foot or so, the momentum from that move will carry the arms and club to the completion of the backswing without any lift requirement.
If this occurs properly, the arms will be tension free at the start of the downswing, and they will properly dead-fall and enable an effortless turn of the body’s core. When the backswing starts slowly, there will be an involuntarily lift to complete the backswing, and tension created by the lift will leave the arms tight in the transition. Having tight arms and shoulders will prevent them from falling into the start of the downswing as they naturally should. If they are stuck at the top do to a lift, an involuntary pull will occur starting down, the core’s turn will be impeded, the club will leave its plane, and the shot will most likely be miss-hit.
Do the “Gravity” Golf Cross Footed Drills; they will teach you to start the swing into motion correctly, and your transition will be smooth and effortless.