Experimental validation of a subject-specific maximum endurance time model

Abstract

This study aimed at experimentally validating a subject-specific maximum endurance time (MET) model. Thirty health participants (15 males and 15 females; Age: mean = 21.5 years, SD = 1.6 years) volunteered to conduct an isometric elbow flexion task until exhaustion. The endurance times of each participant were measured under relative exertion levels ranging from 30% MVC (Maximum Voluntary Contraction) to 70% MVC at 10% intervals. Assessment of the model showed that the intensity–endurance time relationship for each studied individual could be well fitted by the subject-specific MET model (R² > 0.89). The fatigue rates identified from the model fitting were normally distributed (Mean = 0.96 min⁻¹, SD = 0.29 min⁻¹). In addition, the fatigue rates of the male group were significantly higher than the female group. The subject-specific MET model can be used to predict the MET for individual workers, and further support physical task design, based on the fatigability data of a targeted worker population.

Practitioner Summary: Ergonomists have extensively used MET models in physical fatigue assessment and physical task design. A subject-specific MET model could be used to predict the MET at individual levels, and also to support work design for a target worker population, based on the fatigability data distribution obtained from sampled workers.

Keywords:

• Maximum endurance time (MET)
• Subject-specific MET model
• elbow flexion
• fatigability
• physical fatigue

Acknowledgements

The authors thank all volunteers who participated in the study and the AQSIQ Key Laboratory of Human Factor & Ergonomics (China National Institute of Standardization) for their support of experiment equipment and site.