“Early extension” needs to be dropped from the vocabulary. First of all, it implies that hips are the problem. They are not. The problem, or “disease”, is the entire posture lifting as part of an amazing vestibular system reflex that allows the golfer to make impact with what they are looking at. If it were not for “early extension“, most golfers would never make ball contact.
The root cause of this posture lifting is from releasing the club too soon because of the instinct to swing with the arms. We are born wanting to throw objects with our arms and hands. That is why golf is so difficult. One does not throw the golf club. The club follows in a passive manner as the body turns.
To fix early extension, one has to realize that the body turns and pulls the arms. The hips have to start the sequence. The center of gravity of the torso also has to get ahead of the ball.
This concept of early extension is a simplistic and misleading way of looking at the most common problem in golf. It was started by chiropractors at TPI. The term should be abandoned.