A lumbar extension machine is disclosed including a seat with an upright rotatable back member securable to a variable resistance module or statically secured to a load cell module. A lower body system is provide to optimize the exercise of the lower back by preventing movement and work by the hips and thighs. A pelvic restraint pad is located adjacent the seat and the seat is adjustable at the pad to insure that the iliac crest is properly located at the pad. An adjustable foot rest is provided to align the thigh with the seat angle after the seat height has been properly adjusted. The load cell provides strength testing to allow the clinician to determine relative strength and establish treatment parameters and monitor treatment progress and validate and quantify treatment results.