Improved detection of submaximum effort in upper extremity strength and strength-endurance performance testing

This study was a continuation of 2 investigations into methods used to help discriminate between maximum and submaximum effort in maximal power grip (strength), and repeated maximal power grip (strength-endurance). The purpose was to identify valid discriminator variables, which in combination would improve the detection of submaximum effort over single discriminator variables. Three discriminator variables were identified for power grip strength, and also for power grip strength-endurance, A criterion test was developed where the criterion for intentional submaximum effort was greater than or equal to two positive discriminator variables and the criterion for a maximum effort was less than or equal to one positive discriminator variable in both power grip strength and strength-endurance. The criterion test correctly identified 100% of healthy control workers (n = 26) applying maximum effort in power grip strength and strength-endurance; and correctly identified a total of 20 out of 24 (83.3%) submaximum tests for workers purposefully restricting their performances. The criterion test was also applied across the power grip data for a retrospective sample of 51 Workers Compensation patients with unilateral upper extremity injuries, classifying 17 patients (33.3%) as submaximal when using their unaffected limbs. Combinations of multiple discriminator variables were found to improve detection rates for submaximum effort when compared to using single discriminator variables.