15. Light dumbbell exercises are the last worthless exercise on this list. The biggest problem about light dumbbell exercises is that you will spend a lot of time doing completely non-effective movements with them. There are many women who worry that heavy lifting will transform them into bodybuilders, but that wont happen if you know what you are doing with those heavy weights. So stop wasting your time on light dumbbells and start noticing some change on your body!