Reliability and Validity of the Belt-Stabilized Handheld Dynamometer in Hip- and Knee-Strength Tests

Context: The belt-stabilized handheld dynamometer (HHD) has been used to assess the strength of knee- and hip-muscle groups. However, few researchers have examined its reliability and validity for assessing the strength of these muscles.Objective: To evaluate the intra-examiner reliability of the belt-stabilized HHD and its validity and agreement with the isokinetic dynamometer for assessing the strength of knee- and hip-muscle groups.Design: Cross-sectional study.Setting: University laboratory.Patients or Other Participants: We evaluated 26 healthy participants (13 men, 13 women; age 23.5 ± 2.8 years, height 1.7 ± 0.1 m, mass 68.6 ± 12.4 kg) in 2 sessions using the belt-stabilized HHD and an isokinetic dynamometer for maximum strength of the hip adductors, abductors, flexors, extensors, internal rotators, and external rotators and the knee flexors and extensors.Main Outcome Measure(s): We used reliability values provided by the intraclass correlation coefficient (2,3), standard error of measurement (SEM and percentage SEM), and minimal detectable change; correlation values comparing the belt-stabilized HHD and the isokinetic instrument using the Pearson correlation coefficient (r); and the mean difference in values comparing the 2 instruments using the Bland-Altman method.Results: The intrarater HHD reliability was excellent for most measurements (range 0.80–0.96; SEM 1.3–5.3 kilograms of force or 4.8−18.9 Nm, percentage SEM 7.0–22.0, minimal detectable change 3.6–18.8 kilograms of force or 13.2−52.4 Nm) and was moderate only for bilateral knee flexion and left hip internal rotation (intraclass correlation coefficient 2,3 0.62–0.66 and 0.70, respectively). Correlation with the isokinetic dynamometer was moderate to high (r 0.60–0.90), but the absolute values did not demonstrate concordance between results using the Bland-Altman method.Conclusions: The belt-stabilized HHD measurements were reliable, and although they did not agree with those from the isokinetic dynamometer, the values were correlated for the hip- and knee-muscle groups.