The close-stance dumbbell front squat is a popular exercise for targeting the muscles of the lower body, the quadriceps in particular. Holding dumbbells in the racked position also works the core and upper-back muscles to maintain posture while the lower body moves. Because the amount of weight you can use will be limited by what you can clean to the rack position, this movement is usually performed for moderate to high reps, at least 8-12 reps per set or more. If this movement hurts your knees, try performing it with a wider stance.