Get in an amazing workout by incorporating these unique strength-training moves — they only use one dumbbell. Some of these exercises work both sides of the body at once, while others target one side at a time, which may reveal to you which parts of your body are weakest. This will help to strengthen your body more efficiently to prevent injury. One-sided moves also require you to focus on your balance, which automatically fires up the muscles in your core. Have a few dumbbells on hand (five to 25 pounds) and switch them up as needed.