System, method and apparatus for carrying out isometric exercises for either diagnostic purposes or therapeutic purposes. When employed in a diagnostic mode, the instrument is programmed to carry out standardized diagnostic regimens and during such regimens provides both visual and aural cues, carries out mathematical computations of force values and provides recordation of diagnostic data in archival memory. When employed in a therapeutic mode the apparatus may only be programmed within mandated therapeutic parameter limitations. During therapeutic trials, the user is visually and aurally cued throughout the test sequence and the therapeutic data evolved during the regimen is recorded and recoverable from archival memory.