Formulation of perceived muscle fatigue based on elbow flexion task

Abstract

Muscle fatigue should be quantitatively evaluated in order to design an optimum work environment and work-rest scheduling and prevent musculoskeletal disorder of workers. The aim of this study was to formulate a relationship for the dependence of perceived muscle fatigue (PMF) on time and external load. Three differential equation models―saturate, non-saturate, and hybrid of saturate and non-saturate―were proposed for the PMF function. An elbow flexion task was performed with varying load amplitude (percent of maximum voluntary contraction, %MVC), and the PMFs were measured every 30 s during the task execution. The three models were applied to the measured PMFs and compared in terms of their PMF prediction accuracy. In addition, the maximum endurance times (METs) predicted by the three models were compared with the existing MET models. The measured result showed that the PMF increased logarithmically at the relatively low %MVC and linearly at the relatively high %MVC. The hybrid model was selected for the PMF function, because it showed a better fit to the measured PMFs and a higher interclass correlation with the existing MET models. Individually approximated PMF functions for males and females did not show an improved accuracy compared with the PMF function for both genders. Therefore, a single PMF function was applied irrespective of the gender.

Keywords

• ergonomics
• human engineering
• muscle fatigue
• maximum endurance time
• psychophysiology
• modeling
• work environment design
• optimization