Feigned Effort Research Articles

Standard and Short RoM Isokinetic Testing: Comparative Analysis in Identifying Submaximal Shoulder External Rotator Effort

ABSTRACTAn isokinetic-related parameter termed the difference between eccentric-concentric strength ratios at two distinct test velocities (DEC) based on 60° (standard) range of motion (RoM) has been proven to be highly efficient detecting feigned muscular efforts. This study aimed to verify whether a DEC derived from a much shorter test RoM (20°) was equally useful than a long RoM–derived one. Eighteen healthy men (32.4 ± 6.4 years old) took part in a study focusing on shoulder external rotation isokinetic strength. Participants performed a genuine shoulder external rotator maximal effort (eight pairs of concentric and eccentric contractions at high and low velocities at short and long RoM) and then instructed to feign maximal effort. Contraction velocities were adjusted accordingly by applying a 1:4 gradient and peak moments registered. Both condition DEC was then calculated by subtracting the eccentric and concentric strength ratios at low velocities from those at high velocities. DEC scores in the feigned effort were significantly higher than maximal effort ones in both conditions in men. It enabled the setting of specific cutoff levels for separating the efforts. Both approaches revealed a coincident sensitivity (78%) whereas short RoM showed an even higher specificity: 88% versus 78%. Thus, the short RoM protocol provides clinically acceptable detection power.

Identifying Sincerity of Effort Based on the Combined Predictive Ability of Multiple Grip Strength Tests

Study DesignRetrospective Cohort. IntroductionDetecting sincerity of effort (SOE) of grip strength remains a frustrating and elusive task for hand therapists because there are no valid, reliable, or widely accepted assessments for identifying feigned effort. Some therapists use various combinations of different SOE tests in an attempt to identify feigned effort, but there is lack of evidence to support this practice. PurposeThe present study examined the ability of a combination of three grip strength tests commonly used in the clinic to detect SOE: the five rung grip test, rapid exchange grip test, and coefficient of variation. A secondary purpose was to compare the predictive ability between the logistic and linear regression models. MethodsHealthy participants (n=146) performed the three SOE tests exerting both maximal and submaximal efforts. We compared the ability of two regression models, the logistic and linear models, to predict sincere versus insincere efforts. ResultsCombining the three tests predicted SOE better than each test alone. Yet, the full logistic model, which was the best predictor of SOE, explained only 42% of variance and correctly classified only 58% of the efforts. ConclusionsOur findings do not support the clinical practice of combining these three tests to detect SOE. Level of EvidenceNot applicable.

Accuracy of visual estimation in classifying effort during a lifting task

The objective was to determine if visual estimation of effort (VEE) during lifting tasks is accurate in classifying relative levels of exertion or distinguishing between incomplete lifts that may be potentially unsafe and incomplete lifts of "actors" feigning weakness. A convenience sample of 117 health professionals and lay subjects participated in the study. Four actors were videoed performing four complete dynamic lifts (sets of five repetitions) of varying levels of exertion (relative to subjects' physical maximum). Subjects viewed the videoed performances, presented in no apparent order, attempting to properly classify the lifting tasks. For the four levels of exertion, participants were to judge if the lifts were 25%, 50%, 75% and 100% of each actor's maximum lifting capacity and to distinguish between an incomplete (failed) lift of 110% of maximum and a feigned failure of a lift of 25% of maximum. Accuracy for in classifying all lifting activities was marginally higher than chance. There were no differences in the accuracy of health professionals or lay subjects. The VEE does not accurately classify relative levels of exertion or distinguish between incomplete feigned effort lifts and lifts that are potentially too heavy to safely lift.

Cervical circumduction in normal subjects: a study of maximal versus feigned effort.

The feasibility of using the coefficient of variation in conjunction with motion parameters derived from head circumduction to obtain a compact criterion for differentiating maximal from feigned cervical motion was evaluated. Twenty-five healthy subjects were measured twice during a period of 3 weeks using an ultrasonography-based motion analysis system. Subjects were asked to produce maximal motion of the spine as well as to feign limitation. Extracted from the displayed traces of head circumduction, the angular values of the primary motions of flexion, extension, right and left lateral flexion, as well as their additive score (AS) were determined. No test-retest differences were indicated. The average range of motion (ROM) was significantly smaller and the coefficient of variation of the ROM was significantly larger in the feigned compared with the maximal performance in both tests. However, tolerance interval analysis indicated that the coefficient of variation could not effectively separate between the effort levels, being particularly deficient with respect to AS. In addition, a differential sensitivity in identifying false-negative cases as a function of the movement paradigm was revealed. This study indicates that in healthy subjects, the use of a complex cervical movement such as circumduction cannot serve for differentiating between maximal and feigned performance using the coefficient of variation. The results may also point out the existence of a mechanism for adjusting proportional reductions among the primary cervical motions that result in excellent repeatability even in feigned efforts.

Identification of feigned grip effort using isokinetic dynamometry

Objective. To investigate the feasibility of applying isokinetic dynamometry for identifying submaximal grip strength. Design. Measurement of maximal and feigned concentric and eccentric strength 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 related to isometric efforts. This study is based on recent research which has indicated that isokinetic dynamometry was highly efficient in identifying feigned efforts in other major muscle groups. Methods. Seventeen healthy women aged 20–25 took part in the study. Prior to 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 weakness 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 effectively 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 inability to adjust the eccentric and concentric force components during submaximal efforts is probably a general feature. Relevance Isokinetic dynamometry is a powerful method for quantifying various aspects of muscle performance. However, its application in the medicolegal area of muscle weakness has only recently been explored. Combined with previous research, this study strongly indicates that if certain trauma or pathology-related weakness does not result in variations in the force-velocity characteristics of the affected muscles, than this technique has the potential to validly differentiate between patients who have a genuine reason for compensation and those (‘symptom magnifiers’) who do not.

Reproducibility of performance and certainty of judgment in maximal vs feigned muscular effort.

Detection of feigned muscular effort is a highly challenging topic in the medicolegal arena. Modern dynamometric methods have enabled a much higher accuracy in deciding whether the effort in question is indeed genuine or submaximal. Since in feigning the target, however, performance may fluctuate even within a single testing session, reproducibility cannot be assured. In actual claims, the statistical nature of certainty in proclaiming a feigned effort must be well understood by those involved in deciding the fate of a claim.