Modeling of the maximum endurance time of coal miners muscle fatigue for one-handed carrying tasks

Abstract

To prevent safety production accidents caused by muscle fatigue among coal miners, a modified model of maximum tolerance time (TME) was established to predict the TME for one-handed handling tasks. Thirty-one participants including different types of coal miners volunteered to participate in one-handed handling of oil drums for loading, unloading and horizontal walking operations. The maximum voluntary contraction strength (fMVC), subjective fatigue rating (Erp) and TME of coal miners' backs and legs were measured before and after handling operations, as well as during the three task phases. An Erp one-dimensional linear regression prediction model was established under the effect of individual factors. A simplified TME prediction model was developed using power and exponential functions in the relative role of fMVC. A TME-modified model was further constructed considering the effects of weight and heart rate of coal miners. It was found that when fMVC ≤ 0.12, the simplified power model (median function model) provided higher estimates than the exponential model, and the predictions were closer to the true values. With fMVC < 0.2 or lower, incorporating indicators of instantaneous heart rate and body weight of coal miners, the TME modified model was used to accurately assess the TME of coal miners. It is suggested that workers engaged in manual handling operations on a daily basis should not carry a maximum weight of more than 22 kg on the back or legs to avoid musculoskeletal disorders that could lead to safety accidents.