If you have a rounded swing, or 1-Plane swing, you will be more effective using your body rotation as your engine while limiting the amount of arm and hand motion through the impact zone. To make this swing work consistently, you must learn to start the swing so that the body is turning and the arms know their role in the back swing. If the back swing breaks down for a rounded player, it is very common the golfer to have the arms take over the swing which is not what makes this type of swing work well. A rounded swing works well when the body is the dominant power source and the arms are playing a supportive role. That said, the arms MUST work correctly during the take away to allow the body to be in control.
This video is designed to help you make the correct move with the arms and body to make this swing work effectively and repetitively.