Magnitude and reliability of hand-held dynamometer measurements within and between days

The purpose of this study was to compare the magnitude and describe the reliability of repeated measurements of elbow flexion force obtained within and between days with a hand-held dynamometer (HHD). A total of 33 healthy subjects (14 men and 19 women with a mean age of 29.9 years) performed three maximal elbow flexion trials on each of three non-consecutive days. A digital HHD registered the peak force of each trial. Analysis of variance revealed that the measured forces did not differ significantly between trials, but that the forces did differ significantly between days (F= 4.541, P= 0.014). Across days, the force decreased linearly (F= 8.038, P= 0.008). The measurements were reliable within days [intra class correlation coefficient (ICC) = 0.98–0.99] and between days (ICC = 0.987). Although clinicians can be confident that consistent measurements of relatively high muscle forces can be obtained with a HHD, they should establish their own capacity to obtain reliable measurements with the HHD.