Fatigue is a common experience in our daily life and in therapeutic exercises. Human muscle fatigue has been studied using a wide variety of exercise models, protocols and assessment methods. This study conducts quantitative evaluation of fatigue of knee extensor with surface electromyography and dynamometer and is to provide basic materials in physical therapy diagnosis and assessment of skeletal muscle. Measurement of two stages was conducted with 88 normal adults between their twenties and seventies, correlations and differences using collected data according to age was compared and correlations among measured items were analyzed and then the following conclusions were obtained. Analysis of sEMG and dynamometry of knee extensor showed that MDF, FI, MVIC, ET had the closest relations with age and MDF, FI, MVIC were significantly increase with aging. In addition, it was found that there were high correlation among items of analysis.