Test-retest reliability of isometric ankle plantar flexion strength measurement performed by a hand-held dynamometer considering fixation: examination of healthy young participants.

[Purpose] This study aimed to investigate the test-retest reliability of isometric ankle plantar flexion strength measurements performed by a hand-held dynamometer (HHD) using two belts and a newly devised fixation plate. [Participants and Methods] The participants were 83 healthy individuals (female, n=31; male, n=52) with an average age of 20 years. An HHD (μTas F-1) sensor was fixed using two belts and a newly developed metal device to the measurement site on the dominant foot of a participant who was in a sitting position. Measurements were performed twice for each participant. [Results] The average value was 65.6 kgf (bodyweight ratio, 127.3%) for female and 88.0 kgf (136.9%) for male participants. The intraclass correlation coefficients of the two measurements were 0.915 for female and 0.938 for male participants. The minimum detectable change at 95% was 10.1 kgf (12.1% of the average value) for female and 12.1 kgf (15.4%) for male participants. [Conclusion] The test-retest reliability of measuring the ankle plantar flexion strength performed by an HHD using a belt and plate is high. Therefore, the increase or decrease in muscle strength should be judged based on the minimal detectable change with 95% confidence.