Aaron Small, Master Personal Trainer Athletic Club Northeast: Gym Smarts: Lower Body Leg Press Leg press machine. You order strengthen your gluts, quads and hamstrings. What you would do is put your feet up and you push upward this way. You don’t want to lock your knees like that, that could cause a knee injury. Keep your knees unlock. You want to bring it slowly down before the weight stack hits, in a slow smooth fashion.