Identifying sincerity of effort by grip strength ratio of three wrist positions in individuals with upper extremity musculoskeletal disorders

OBJECTIVES: To evaluate whether the grip strength ratio of three wrist positions could determine sincerity of effort (SOE), by differentiating between maximal effort (ME) and submaximal effort (SE), in individuals with upper extremity musculoskeletal disorders (MSDs). METHODS: A total of 19 volunteers with unilateral upper extremity MSDs (9 males, 10 females) participated in this study. Participants performed grip strength tests in neutral, full flexion, and full extension wrist positions for both hands. In each wrist position, they exerted grip force with their ME and preferred SE for three times. RESULTS: Significant main effects of type of effort, wrist position (P < .001), and hand (P = .005) were observed. The results also showed significant interactions for type of effort × wrist position (P < .001) and wrist positions × hand (P = .001). Moreover, the grip strength ratios of neutral/flexion (N/F) and neutral/extension (N/E) between ME and SE differed significantly (P < .001). CONCLUSION: This study suggests that the N/F and N/E grip strength ratios can discriminate between ME and SE in individuals with upper extremity MSDs. Thus, this test might be applicable to use for identifying SOE in clinical setting.