Determination of subject-specific muscle fatigue rates under static   fatiguing operations
  Cumulative local muscle fatigue may lead to potential musculoskeletal disorder (MSD) risks {\color{red}, and subject-specific muscle fatigability needs to be considered to reduce potential MSD risks.} This study was conducted to determine local muscle fatigue rate at shoulder joint level based on an exponential function derived from a muscle fatigue model. Forty male subjects participated in a fatiguing operation under a static posture with a range of relative force levels (14% - 33%). Remaining maximum muscle strengths were measured after different fatiguing sessions. The time course of strength decline was fitted to the exponential function. Subject-specific fatigue rates of shoulder joint moment strength were determined. Good correspondence ($R^2>0.8$) was found in the regression of the majority (35 out of 40 subjects). Substantial inter-individual variability in fatigue rate was found and discussed. 
Liang Ma (IRCCyN, DIE), Wei Zhang (DIE), Bo Hu (DIE), Damien Chablat   (IRCCyN), Fouad Bennis (IRCCyN), Fran\c{c}ois Guillaume
cs.RO