A device for resistance exercise of muscle groups that cross two or more joints such as biceps group, triceps group, quadriceps group, and hamstring group. The device comprises a primary cam or gear fixed non-rotatably to the frame of an appropriate exercise machine for working the desired body part,...http://www.google.es/patents/US7645216?utm_source=gb-gplus-sharePatente US7645216 - Dual cam exercise device method and apparatus
