Research

Schapmire D, St. James JD, Townsend RT, Feeler L.  Accuracy of Visual Estimation in Classifying Effort During a Lifting Task.  Accepted for publication in Work, A Journal of Prevention, Assessment and Rehabilitation.

Objective: 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.  Participants: A convenience sample of 117 health professionals and lay subjects participated in the study.  Methods: 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.  Results: 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.  Conclusion:  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.          

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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Objectives:  1. To determine if scores on pain questionnaires and overt behaviors during a functional capacity evaluation (FCE) were related to variability between repeated measures during a hand strength assessment.  2. To determine if failure of statistically-based validity criteria, as proposed by Schapmire, St. James and Townsend et al. is likely to be due to pain.  Participants:  200 consecutive clients presenting for an FCE.  Methods:  Subjects filled out pain questionnaires, were observed for various behaviors and were administered the distraction-based hand strength assessment.  Results: Clients 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 <.001, 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 clients and for normal subjects feigning weakness in a controlled study (p > .05).  Conclusions:  Pain does not reasonably explain the failure of the statistically-based validity criteria.  The protocol is appropriate for use in a client 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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Objective:  To determine if passing or failing statistically-based validity criteria during a distraction-based hand strength assessment is related to test behavior during a lifting assessment. Participants:  200 consecutive clients presenting for an FCE.  Methods:  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.  Results:  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 .014 for right and left unilateral lifts, respectively, and p < .0005 for three different bilateral lifts.  Conclusions:  A pattern of performance related to the degree of variability in repeated measures protocols for these two distraction-based protocols is revealed.  Passing or failing the hand strength assessment are each equally predictive of test outcome during the distraction-based lifting assessment.  The failure of the validity criteria in these two distraction-based tests cannot be attributed to a history of surgery but, rather, is the result of abnormal test behavior.   

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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Objective:  To determine if isometric (static) strength accurately predicts dynamic lifting capacity.  Participants:  107,755 male and 23,078 female prospective workers taking part in a post-offer employment test.  Methods: Subjects were tested for strength three standard static lifts and attained physical maxima for four dynamic lifts.  Results:  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.  Conclusions:  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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Objective:  The purpose of this study was to determine if these two commonly-administered isometric tests are accurate indices of effort.  Participants: 34 healthy subjects were tested once giving a maximum voluntary effort and once attempting to feign weakness of 50% of maximum.  Results:  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.  Conclusions: Neither isometric lift is appropriate for classifying validity of effort.  Use of these isometric lifts should be discontinued for the assessment of effort.