There are literally hundreds of exercises you can do in the gym or at home. Some you love; some you hate. Some work; some don't. You can find any number of videos online with moves that the trainer, expert, or guru says you have to try. The truth is there are probably some exercises you shouldn't be doing — or ones you should do instead. We spoke with certified personal trainer Heather Neff and got her list of the top three moves she has her clients avoid and what to do instead.