The lunge exercise strengthen the quadriceps muscles, gluteal muscles and the hamstrings muscles. A long lunge focuses on the gluteal muscles and a short lunge focuses on the quads. Standing comfortably with the feet apart, step forward heel-first and continue the momentum until a knee flexion angle of 90 degrees and directly above the toes, not further. The back knee should also feel the stretch. Push up with the front leg to return to the standing position.