  The increase of surface electromyography (sEMG) root-mean-square (RMS) is
very frequently used to determine fatigue. However, as RMS is also influenced
by muscle force,its effective usage as indicator of fatigue is mainly limited
to isometric, constant force tasks.This research develops a simple me-thodto
preclude the effect of muscle force, hereby estimates the EMG amplitude
response exclusively to fatigue with RMS. Experiment was carried out on the
biceps brachiis of 15 subjects (7males, 8 females) during sustained static
maximum voluntary contractions (sMVC).Result shows that the sEMG RMS response
to fatigue increasesto 21.27% while muscle force decreasing to 50%MVC, which
implies that more and more extra effort is needed as muscle fatigue
intensifies. It would be promising to use the RMS response exclusively to
fatigue as an indicator of muscle fatigue.
