Abstract: The object of the invention is a method for determination of endurance and sensitivity to fatigue of a muscle. In this method one or more recording electrodes are placed on top of the muscles to be tested from the test subject and the action potentials of the muscle cell membrane of a muscle are measured by recording electrodes and equipments. It is difficult to define the endurance and sensitivity to fatigue of a person's muscles in comparison with the general population. In the method according to the invention a frequency analysis, the so-called FFT-analysis, is performed to the recorded EMG-signal, and by using this analysis with three or more calculation parameters the lowering of the conduction rate of a muscle cell membrane is observed as well as the rate of change of the calculation parameters as a function of time, and a comparable value is obtained which indicates the endurance and sensitivity to fatigue of a muscle.