This: stop with the implement more or less overhead. Swinging it from all the way back is way too much effort for what little you might gain. And bend the knees more on the downstroke. You'll get more power into the swing. A strong swing uses the whole body efficiently. Should be on your toes at the top of the swing. Whole body to get the implement to the top of the swing, whole body to bring it down. Distribute that load!