Test-Retest Reliability of Isometric Leg Muscle Strength Measurements Made Using a Hand-Held Dynamometer Restrained by a Belt: Comparisons during and between Sessions

[Purpose] The aim of this study was to evaluate the test-retest reliability of isometric muscle strength measurements made using a hand-held dynamometer restrained by a belt. [Subjects] The subjects were 37 healthy adults (18 men and 19 women) with a mean age of 21.9 years. [Methods] Measurements were made on the dominant leg using a hand-held dynamometer (μTas MF-01 or F-1, Anima Corp., Tokyo) and a belt to fix the position of the body part under test. The strengths of the following 10 muscle groups were evaluated: flexors, extensors, abductors, adductors, internal rotators and external rotators of the hip; flexors and extensors of the knee; and dorsiflexors and plantar flexors of the ankle. Each measurement was repeated after at least 30 seconds of rest in three sessions: in the morning, in the afternoon on the same day, and one week later. [Results] The intraclass correlation coefficient (ICC) for the first and second sets of measurements made in each session ranged from 0.75 to 0.97. ICC for the highest measurements of each muscle group in each of the three sessions ranged from 0.56 to 0.91. [Conclusions] The test-retest reliability of isometric muscle strength measurements of the lower limb made using a hand-held dynamometer equipped with a stabilizing belt varies widely, depending on the muscle action tested, and it would be better to repeat the measurements on different occasions.