Research

Abstract: The detection of feigned weakness in hand-grip strength assessment is difficult. We review several proposed methods and their weaknesses. A comparison of unilateral testing and simultaneous bilateral testing with the Jamar™ dynamometer and the Baseline™ pinch gauge is demonstrated as a solution. An experiment employed 100 asymptomatic subjects tested twice, once under instructions to give a full effort and once under instructions to feign weakness. Seven statistical criteria of noncompliance were chosen. Defining noncompliance as failing two or more of the seven criteria, 99% of the instructed-noncompliant subjects were correctly classified as noncompliant. No subjects were incorrectly classified as noncompliant during instructed compliant testing. Twelve subjects failed a single criterion. On retesting, all but one were correctly classified. One subject in the instructed-noncompliant group passed all criteria. Including retesting of the 12 "grey-zone" subjects, accuracy was 99.5%.

Schapmire D, St James JD, Feeler L, Kleinkort J. Simultaneous Bilateral Hand Strength Testing in a Client Population, Part I:  Diagnostic, Observational and Subjective Complaint Correlates to Consistency of Effort.  Accepted for publication in Work, A Journal of Prevention, Assessment and Rehabilitation. 

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Abstract: This is a retrospective cohort study of 200 consecutive insurance claimants who were tested during a functional capacity evaluation (FCE).  Past study of normal subjects proposed simultaneous bilateral testing of the hands as a method of classifying effort as described by  Schapmire, St. James and Townsend et al. but no subsequent studies have assessed the applicability of the methodology to a patient population.   The purpose of this study was twofold:  to assess the observational correlates to test classification and to determine if “pain” is likely to account for a failure of the validity criteria.  Subjects filled out pain questionnaires, were observed for various behaviors and were administered the distraction-based hand strength assessment.  Patients failing two or more of the statistically-based validity criteria had higher scores on most pain questionnaires, presented with a higher frequency of various pain behaviors (p < .05 and <.0004, respectively), and had a lower rate of relevant surgeries (p < .001). There was no statistically significant difference in the number of failed validity criteria between this group of patients and for normal subjects feigning weakness in a controlled study (p > .05).  The protocol is appropriate in a patient population.

St James JD, Schapmire D, Feeler L, Kleinkort J. Simultaneous Bilateral Hand Strength  Testing in a Client Population, Part II: Relationship to a Distraction-Based Lifting Evaluation. Accepted for publication in Work, A Journal of Prevention, Assessment and Rehabilitation. 

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Abstract: This is a retrospective cohort study of 200 consecutive insurance claimants undergoing a functional capacity evaluation.  The purpose of this study was to determine whether a pattern of test behavior in one distraction-based test for the hands (involving simultaneous testing of both hands) predicts test behavior in a distraction-based lifting assessment when workloads are lifted on a second class lever arm.  The two testing protocols, one involving a hand strength assessment, the other involving an assessment of lifting capacities, were administered to assess the variability between repeated measures.  Clients failing two or more statistically-based hand strength validity criteria had significantly more variability between repeated measures in the lifting assessment, p = .001 and p =.014 for right and left unilateral lifts, respectively, and p <.001 for three different bilateral lifts.  The test outcome in one protocol (passing or failing the validity criteria.) is predictive of test behavior in the other.   

Feeler L, St. James JD, Schapmire D.  Isometric Strength Assessment  I: Static Testing  Does Not Accurately Predict Dynamic Lifting Capacity.  Accepted for publication in Work, A Journal of Prevention, Assessment and Rehabilitation. 

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Abstract:  Published studies have generally found modest correlations between isometric and dynamic measures of strength.  Various systems for functional capacity evaluation and post-offer testing that are currently marketed rely on isometric testing to determine whether workers are able to perform specific job duties, including dynamic lifting.  Results of post-offer employment testing for 107,755 male and 23,078 female prospective workers are reviewed to determine if isometric strength measurements can be used to predict dynamic lifting capacity.  Subjects were tested for three standard static lifts and attained physical maxima for four dynamic lifts.  The data confirms modest correlations between isometric and dynamic measures.  However, the standard errors of estimate for all isometric-to-dynamic predictions make such predictions meaningless for the practical purpose for which they are most commonly used.  The Static Leg Lift, Static Arm Lift and Static Back (Torso) Lift are not appropriate for making predictions relative to dynamic lifting capacity.  Given the likely degree of error in such predictions,  and in light of potential safety concerns as reported by previous investigators, employers, clinicians and risk managers now have substantial objective evidence to call such testing into question.

Townsend R, Schapmire D, St. James JD, Feeler L.  Isometric Strength Assessment II: Static Testing Does Not Accurately Classify Validity of Effort.  Accepted for publication in Work, A Journal of Prevention, Assessment and Rehabilitation. 

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Abstract: Isometric strength testing has been promoted as a type of physical test that can be used to assess sincerity of effort.  An extensive search of the literature finds no controlled studies in which two static lifts, the Static Arm Lift and Static Leg Lift are found to be either sensitive or specific in classifying validity of effort.  The purpose of this study was to determine if these two commonly-administered isometric tests are accurate indices of effort.  In this controlled study, 34 healthy subjects were tested once giving a maximum voluntary effort and once attempting to feign weakness of 50% of maximum.  During feigned weakness sessions, 20 of 34 subjects (58.5%), produced CVs of 15% or less during the Leg Lift.  At the 95% CI, the expected frequency of false negatives for feigned weakness is 42.3 to 75.3% for the Leg Lift.  At the 95% CI, the expected frequency of false negatives for feigned weakness is 51.9% to 83.3% for the Arm Lift.  Neither isometric lift is appropriate for classifying validity of effort.  Use of these isometric lifts should be discontinued for the assessment of effort.