Examination and reliability of measuring muscle strength of ankle plantar flexion with knee extended

[Purpose] A hand-held dynamometer (HHD) is less expensive than the isokinetic muscle strength measurement device, and research using HHD is gradually increasing. However, measurement is performed only at a low muscle strength level at which the heel does not take off or heel detachment occurs; therefore, fixation of the foot becomes a problem. This study aimed to determine the validation of measuring ankle plantar flexion strength (with the knee extended) using HHD. [Participants and Methods] Twenty healthy adults (14 males and 6 females) participated in this study. The chair used in this study was for swallowing videofluorography, which was fixed to a wall bar by the belt. The sensor was located at the third metatarsal head. After warming up, the participants sat in a long sitting position on the chair. We conducted the test two times. We used intraclass correlation coefficient (ICC) and Bland–Altman analysis to assess reliability. [Results] The ICC(1, 1) and ICC(2, 1) results were all greater than 0.9. No fixed and proportional errors were present. [Conclusion] The measurement method of this study was both intra- and inter-examiner reliabilities, which were high, and we suggest that sufficient clinical application is possible.