Identification of feigned shoulder flexion weakness in normal subjects.

Abstract

The purpose of this study was to compare the effect of three related test protocols on the power of a specific index relating to the difference between the eccentric to concentric strength ratios (DEC) to identify feigned shoulder flexion effort. Seventeen normal subjects were instructed to exert maximal concentric and eccentric shoulder flexion effort and then to feign weakness, pretending the presence of a shoulder injury. For both range of motions (ROMs), the DEC scores in the feigned effort were significantly greater than their maximal counterparts. A case by case analysis revealed that the DEC correctly identified 100% of the feigned efforts when derived from the 40 and 160 degrees/sec combination. The findings indicate that the DEC retains its efficiency even under very short muscle length variation as long as adequate velocity gradients are applied. Consequently, maximality of effort may be tested outside compromised ROMs, particularly where pain or instability denies the performance of a standard full ROM protocol.