Body-Solid S2LEC Pro ClubLine Series II Leg Extension / Leg CurlThe leg extension is a vital movement in strengthening your quads and patellar ligament giving your knee added stability. The leg curl trains the often neglected hamstrings protecting you from injury, increasing leg strength, greater flexibility and relief from back pain. Strengthen your quadriceps muscles with the leg extension exercise and work your glutes and hamstring muscles with the leg curl. The transition between the two movements is simple