I call this exercise the glute kickback. And while it may seem like it only focuses on your lower body, it will also work out muscles in your upper body too, as they help you maintain good form. Overall, you’ll work the core and abdominals; lower back, buttocks, hamstrings behind your knees and your upper arm and shoulder muscles. 1. Place a mini-band around your feet. On a flat, firm surface, get on your hands and knees.2. Place...