Lower back curl
How to do it: Lie down flat with your arms by your sides. Slowly raise your chest upwards, with your arms down. Keep your head up during the move. Once you've reached the furthest point up, lower yourself back down.
Why: People often forget the importance of back workouts, but they're vital to develop all other muscle groups. This curl is great as it works the whole back and also alleviates back pain from days at the desk.