Crushing It! is a fun yet grueling combat workout. It's simple yet it recruits all major muscle groups. It demands concentration and a decent amount of coordination. Simple moves + decent numbers + smart circuit = excellent ROI. Mind your form and go slow when doing push-ups. You don't want speed here, you want to focus on your technique and harness gravity to help you hyperload and challenge your muscles.
Extra Credit: Do push-ups as slowly as possible.