This study investigated differences in values of manual muscle tests after exposure to congruent and incongruent semantic stimuli. Muscle testing with a computerized dynamometer was performed on the deltoid muscle group of 89 healthy college students after repetitions of congruent (true) and incongruent (false) self-referential statements. The order in which statements were repeated was controlled by a counterbalanced design. The combined data showed that approximately 17% more total force over a 59% longer period of time could be endured when subjects repeated semantically congruent statements (p < .001). Order effects were not significant. Over-all, significant differences were found in muscle-test responses between congruent and incongruent semantic stimuli.