Detection of submaximal effort by use of the rapid exchange grip

To assist in distinguishing patients with truly decreased hand grip strength from those deliberately not gripping the dynamometer at maximal capacity, a rapid exchange grip strength test was devised and tested under four conditions. Part I, 100 normal subjects undergoing static grip testing and the rapid exchange grip test. Part II, 45 patients chosen at random from physical therapy with various hand injuries tested using only the static grip test. Part III, a blind control study on 15 normal subjects instructed to fake an injury to either the right or left hand. This group was given both the static and rapid exchange grip test. Part IV, a retrospective evaluation of 45 patients seen in a private hand practice who had both the static and rapid exchange grip test. After the dynamometer had been set to the position at which the patient had previously achieved maximal grip strength, the patient was instructed to rapidly alternate hands while gripping the dynamometer. Uninjured subjects had consistently lower rapid exchange grip test scores than previous scores at the same setting (negative rapid exchange grip). Average rapid exchange grip test scores were higher than previous scores (positive rapid exchange grip) when subjects were instructed to fake an injury with one hand. We conclude that if maximal performance has not been achieved on the static test, the rapid exchange grip shows a significant increase in grip strength on the affected side. More patients claiming worker's compensation had positive rapid exchange grips and the average score was higher than that of patients not claiming worker's compensation. This test may help differentiate the patient whose decreased performance is secondary to pain from those who voluntarily perform submaximally.