Comparative Study of Validity and Reliability of Two Handgrip Dynamometers: K-Force Grip and Jamar

Abstract

Background: Handheld dynamometers are used for diagnosis and rehabilitation at several pathologies. Grip force is essential for a person’s quality of life. Most dynamometers are not equipped with rehabilitation or training protocols, although the bibliography highlights this need. Objective: To compare the validity and reliability of Jamar and K-Force Grip dynamometers in patients with shoulder impingement syndrome and healthy people. Methods: Concurrent validity was assessed using known weights. Forty-four (44) patients and 69 healthy adults performed three maximum repetitions in random order with each hand, at each instrument. Reliability was evaluated using ICCs for each instrument separately, and between the two instruments. The differences between the two dynamometers were evaluated using repeated t-tests. Results: Concurrent validity of the two instruments did not reveal fix or proportional bias. Analyses for reliability yield high correlation coefficients for both groups with the lower one being between the two instruments r = 0.90, p < 0.05, (0.72–0.91) for the healthy group. T-tests showed that all participants had lower force values when using the K-Force Grip (p < 0.05). Conclusion: Both dynamometers were reliable in measuring hand grip strength for both groups. K-Force Grip was reliable and valid with respect to Jamar that was used as a benchmark. The different handle dimensions between the two dynamometers may be the reason for the different force values.