Optimal Joint Positions for Manual Isometric Muscle Testing.

CONTEXT Manual isometric muscle testing is a common clinical technique that is used to assess muscle strength. To provide the most accurate data for the test, the muscle being assessed should be at a length in which it produces maximum force. However there is tremendous variability in the recommended positions and joint angles used to conduct these tests, with little apparent objective data used to position the joint such that muscle force production is greatest. OBJECTIVE To use validated anatomically and biomechanically-based musculoskeletal models to identify the optimal joint positions in which to perform manual isometric testing. DESIGN In silico analysis. MAIN OUTCOME MEASURE The joint position which produces maximum muscle force for 49 major limb and trunk muscles. RESULTS The optimal joint position for performing a manual isometric test was determined. CONCLUSION Using objective anatomical models that take into account the force-length properties of muscles, we identified joint positions in which net muscle force production was predicted to be maximal. This data can help health care providers to better assess muscle function when manual isometric strength tests are performed.