Last but definitely not least, your chest or pectoral muscles round out one of the last key muscles groups that should be targeted in your upper body workouts. Also helpful for good posture and injury prevention, a strong chest, especially in males, is a tell-tale sign of  guys fitness level. The age-old push up and bench press are 2 common exercises that strengthen the pectoral muscles, along with many different machines at the gym these days that target your chest.