Intra-tester and inter-tester reliability of the MicroFET 3 hand-held dynamometer.

Background: The reliability of the MicroFET 3 has not previously been reported in the literature. The aim of this study was to evaluate intra-tester and inter-tester reliability of the MicroFET3 hand-held dynamometer (HHD) in three lower limb muscle groups. Methods: Maximum voluntary isometric contraction (MVIC) of hip extension, knee extension and ankle plantar-flexion were measured in 38 healthy participants (males=18, females= 20) by two testers on separate days using the MicroFET3 HHD. The reliability analysis was carried out using intra-class correlation coefficients (ICCs) to measure association and Band and Altman plots to demonstrate agreement. Results: The results showed that intra-tester reliability was moderate to excellent; with associations ranging from ICC 0.56 - 0.92 and higher agreement for knee and ankle than hip measurements was shown. Inter-tester reliability was lower, with hip and knee associations ranging from ICC 0.60 - 0.66. Ankle measurements intertester associations were particularly low (ICC 0.23 and 0.15). These values would not be considered acceptable for clinical use. Bland and Altman plots used to demonstrate agreement between testers displayed a considerable lack of agreement with discrepancies of up to 150N noted in measurements. Conclusion: The results suggest that the MicroFET3 HHD displayed moderate to excellent intra-tester reliability and poor to moderate inter-tester reliability and agreement with discrepancies noted between muscle groups. While use of this instrument can be recommended when consistently used by a single tester, further reliability analysis should be carried out before this instrument could be recommended for use by different testers in the clinical setting.