Using the “Visual Target Grip Test” to Identify Sincerity of Effort during Grip Strength Testing

We devised a sincerity of effort assessment based on “tricking” a person into exerting maximal effort by providing incorrect visual feedback. The assessment involves deriving a target line from nonvisual peak gripping force, instructing participants to reach it with each grip repetition, and then secretly changing its position, which requires doubling the force necessary to reach it. Accordingly, participants are tricked into exerting more force than intended to reach the deceptive target line. We examined the validity of this test by comparing force values between “trick” and “non-trick” trials in 30 healthy participants. The study design used was a prospective cohort. Providing incorrect visual feedback caused significantly greater increases in force during submaximal effort (69%) than during maximal effort (28%). This test effectively detected submaximal effort (sensitivity = 0.83 and specificity = 0.93). Although this test is not safe for patients during initial therapy, it may be appropriate for patients who can safely exert maximal grip force.Level of EvidenceNot applicable.