Determination of subject-specific muscle fatigue rates under static fatiguing operations
This work addresses the need for personalized fatigue assessment to mitigate musculoskeletal disorder risks in occupational settings, but it is incremental as it applies an existing model to new subject-specific data.
This study tackled the problem of assessing subject-specific muscle fatigue rates during static operations to reduce musculoskeletal disorder risks, by determining fatigue rates at the shoulder joint using an exponential model, achieving good regression fits (R²>0.8 for 35 out of 40 subjects) and revealing substantial inter-individual variability.
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.