Don’t Make This Backswing Mistake
I see a lot of amateurs make this mistake when they hit golf balls (especially with their driver). You want the length of your arms going the same distance back in your back swing as your shoulders tell them to. If they go back farther then that then this is slack.
When you get into your back swing, you want your shoulders to be telling how far back your arms can go, if they go further than this then you have problems. This will result in back swings that are way too long and when this happens then your arms have to catch back up to your body turn on the downswing.
If your back swing is going too far back then you want to start to shorten it up. This will create more consistency and more power. If they are running away from your body then you are going to have to initiate your arms in the downswing and you want to be using your body.