The sensitivity of upper limb muscle moments to variation in physiological cross-sectional area

The sensitivity of a computer-based muscle model is analyzed in a study examining the effects of variations in physiological cross-sectional area (PCSA) and the specific tension of muscle on muscle moments. The maximum isometric force for upper extremity muscles is estimated from specific tension and PCSA sources reported or derived from human cadaver study literature. PCSA, specific tension and other related model parameters are entered into a spreadsheet used to generate muscle moment curves using limb geometry taken from an MRI cadaver study. Specific results are shown for brachialis brachioradialis and pronator teres, but are generalized to other upper limb muscles. The muscle model was shown to be highly sensitive to the wide range of PCSA values apparent in most human populations. Potential educational applications of the muscle spreadsheet software are described. Recommendations are made for collection of similar data in future studies.