One of the best exercises for building quick muscle is the heavy club Barbarian Squat. Simply stated, it’s a full body complex which addresses the legs and glutes like a squat, the traps and back like a deadlift, the shoulders like a pull over and front raise, the arms like a curl and extension, and the core like a medball floor routine.
Few things hit everything like the Barbarian Squat.
Work the Barbarian into your program on your back or leg day if you’re into training body splits. If you train full body complexes every session, use the Barbarian at the beginning to ensure your arms don’t fatigue due to core exhaustion from other movements.