The Validity and the Reliability of Trunk Flexion and Extension Muscle Strength Measurements in the Sitting Position

[Purpose] The purpose of this study was to examine the validity and the reliability of trunk flexion and extension muscle strength measurements made by a hand-held dynamometer (HHD) in the sitting position. [Subjects and Methods] Thirty-four healthy adults were subjects. Measurements made by the HHD were compared with those made by isokinetic strength measurement equipment (ISME). The validity was investigated with Pearson’s product moment correlation coefficient, inter-rater and intra-rater relative reliabilities were estimated using the intraclass correlation coefficients (ICC), and the absolute reliability was determined using Bland-Altman analysis. [Results] HHD and ISME measurements showed a significant correlation, and ICC values were high. The trunk extension muscle strength showed a large bias in Bland-Altman analysis. [Conclusion] Clinical applications of HDD measurements is possible with due consideration of the measurement error.