Identification of feigned grip effort using isokinetic dynamometry

Objective. To investigate the feasibility of applying isokinetic dynamometr y for identifying submaximal grip strength. Design. Measurement of maximal and feigned concentric and eccentric strengt h at high and low contraction velocities. Background. Identification of feigned grip strength is a highly problematic issue which has been challenged using various techniques, invariably relat ed to isometric efforts. This study is based on recent research which has i ndicated that isokinetic dynamometry was highly efficient in identifying fe igned efforts in other major muscle groups. Methods. Seventeen healthy women aged 20-25 took part in the study. Prior t o executing the feigned effort, subjects were told to exert lower than the maximal grip strength in an attempt to obtain financial compensation for a simulated injury to hand musculature which in fact did not result in weakne ss of grip. Results. Findings indicated that based on a parameter termed DEC which was defined as the difference between the ratios of the eccentric to concentric strength at the high and low velocities, feigned efforts could very effect ively be identified (P < 0.0001). Furthermore. a multivariate model enabled this identification to be described in terms of the level of confidence by which a claim concerning weakness of grip may be proclaimed as genuine or insincere. Conclusions. Though the neuromotor mechanisms responsible for grip strength may differ from those acting with respect to other muscle groups, the inab ility to adjust the eccentric and concentric force components during submax imal efforts is probably a general feature.