AbstractIn muscle rehabilitation and training, it is important to evaluate a patient's muscle state. In general, training is based on physical therapy, but there has not been quantitative assessment of the actual effects on muscles. The authors previously tried to quantify muscle fatigue and defined “Muscle‐fatigue time (MFT)” as the quantitative evaluation index of muscle fatigue based on electromyography and the use ratio of the muscle fiber type. MFT is the time when the use ratio of the slow muscle fiber (Type I) and the fast muscle fiber (Type IIb) intersects. Furthermore, the authors also proposed a method to estimate MFT by modeling the relationship between each muscle load and MFT. This paper examines the appropriate evaluation method for MFT containing variation, and generalization performance of the constructed model.