Abstract: A sincerity index system is provided for determining the sincerity of a person undergoing muscular testing. The system includes a muscular force detector for sensing and measuring the force exerted by first muscles upon a predetermined body movement and providing a first signal proportional to the force exerted. An electromyograph senses and measures the bioelectric activity of second muscles corresponding to the first muscles, the electromyograph providing a second signal proportional to the bioelectric activity. An interface device processes the signals and provides at least two factors, and an index-forming program combines the factors in a predetermined manner to provide a sincerity index having upper and lower limits. Using the system one can ascertain faked or exaggerated soft tissue injury, the extent of injury, and the extent of concomitant disabilities.