By now you should have built your clients strength and control up that you can introduce the full chin up. I coach the client to initiate the movement with scapula retraction and depression and aim for full retraction/depression at the top of the movement. A good mental trick is to concentrate on pulling your elbows to your side rather than getting the chin over the bar. It’s good practice to get your clients to create some abdominal bracing to control the swing that occurs if you are too relaxed.
Dave Stewart
The Trainer’s Trainer