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

Abstract

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.

Keywords: lower extremity; muscle strength; reproducibility of results.

Figure 1.

Hand-held dynamometer attached to the isokinetic dynamometer with hook-and-loop straps.

Figure 2.

Belt-stabilized hand-held dynamometer and isokinetic dynamometer tests. A, Knee flexion and extension. B, Hip internal rotation and external rotation. C, Hip adduction and abduction. D, Hip flexion and extension.

Figure 3.

Bland-Altman plots comparing the belt-stabilized hand-held dynamometer and isokinetic dynamometer measurements in assessing torque of the knee extensors and flexors. The P value is for the slope of the regression line. A, Right knee extension (limits of agreement). B, Right knee flexion. C, Left knee extension. D, Left knee flexion. Abbreviation: SD, standard deviation.

Figure 4.

Bland-Altman plot comparing the belt-stabilized hand-held dynamometer and isokinetic dynamometer measurements in assessing torque of hip internal and external rotators and hip extensors. The P value is for the slope of the regression line. A, Right hip internal rotation. B, Left hip internal rotation. C, Right hip extension. D, Left hip extension. E, Right hip external rotation. F, Left hip external rotation. Abbreviation: SD, standard deviation.

Figure 5.

Bland-Altman plot comparing the belt-stabilized hand-held dynamometer and isokinetic dynamometer measurements in assessing torque of hip flexors, adductors, and abductors. The P value is for the slope of the regression line. A, Right hip flexion. B, Left hip flexion. C, Right hip adduction. D, Left hip adduction. E, Right hip abduction. F, Left hip abduction. Abbreviation: SD, standard deviation.