Isometric knee muscle strength measurement using a belt-stabilized hand-held dynamometer and an isokinetic dynamometer with and without trunk fixation: investigation of agreement of measurement values and factors influencing measurement.

[Purpose] The purpose of this study was to examine the agreement between the values obtained by using a hand-held dynamometer with a belt (belt-HHD) and an isokinetic dynamometer (IKD) for the measurement of isometric knee flexion and extension muscle strength. We also studied the factors influencing the measurement. [Participants and Methods] Overall, 26 healthy young adults (16 males, 10 females) participated in the study; the mean age was 21 years. Knee flexion and extension muscle strength were measured by three methods: 1) belt-HHD, 2) conventional IKD with the participant sitting on an attached chair (conv-IKD), and 3) modified IKD with the participant sitting on the same mat table as HHD (mod-IKD). [Results] In the measurement of knee extension, mod-IKD and conv-IKD showed a fixed bias and a proportional bias, conv-IKD and belt-HHD showed a fixed bias, and belt-HHD and mod-IKD showed a fixed bias. In the measurement knee flexion, conv-IKD and mod-IKD showed a proportional bias, belt-HHD and conv-IDK showed a fixed bias, and mod-IKD and belt-HHD showed a fixed bias. In each combination, the measured values were larger in the latter due to errors. However, the types and values of errors differed when analysis was conducted based on gender. [Conclusion] In order to increase the agreement between the values, it is necessary to revise the fixing method of the trunk, and the fixing method of the belt and the sensor pad in belt-HHD.