Using the Force-Time Curve to Detect Maximal Grip Strength Effort

Currently, there are no universally accepted assessment methods for detecting insincere effort during grip strength testing. We examined the validity of the slopes of the force-time curve (during force-generation and force-decay phases) as indicative of sincerity of effort. Thirty healthy subjects performed both maximal and submaximal grip strength trials. The test administrator was blinded as to the nature of the effort. A force-time curve was generated for each individual trial. The slopes of the force-generation phase and the force-decay phase were calculated. Both slopes were significantly steeper for the maximal than the submaximal efforts (p ≤ 0.0001). Sensitivity and specificity analyses revealed that the slope of the force-generation phase was a more effective assessment of sincerity of effort for women, whereas the slope of the force-decay phase was a more effective assessment for men. The most notable finding was that for the force-decay phase, for slope cutoff values of −0.75 and −1.0, none of the men who exerted maximal effort were mistakenly identified as exerting a submaximal effort, whereas only 7% of the men who exerted submaximal effort were incorrectly identified as exerting a maximal effort. Thus, the slopes of the force-time curve are valid and effective in detecting sincerity of effort in healthy subjects. This study represents the first step in establishing the feasibility and validity of a new sincerity of effort assessment using the slopes of the force-time curve. Future research is needed to establish the validity and effectiveness of this sincerity of effort assessment in people with hand injury.