Percentile values for determining maximum endurance times for static muscular work

Abstract

The maximum endurance time (MET) is a key parameter for the ergonomic evaluation of static work. The aim of this study is to offer practitioners MET values in relation to the %MVC (percentage of maximum voluntary contraction) that take into account the results of several studies published on MET. Twenty four published MET models were combined to extract MET percentile values that reflect the interindividual variability and differences among the experimental methods used to develop the models. The MET differences by muscle group are also verified. The results of this study show that, (1) there is a significant difference between the MET values for the back/hip and the MET values for the upper limbs, for a same %MVC value; (2) the model-generated MET values follow a lognormal distribution. A summary table is presented showing the most frequently used percentile values (5th, 10th and 15th percentiles) of the MET corresponding to a range of %MVC values. The data from this paper allow engineers and ergonomics practitioners to design workstations that can accommodate a desired proportion of the worker population, i.e., designs that are not restricted only to the 50th percentile. Relevance to industry Static and intermittent static muscular work is a known risk factor for musculoskeletal disorders (MSD). Estimation of MET to accommodate a percentage of the worker population is a necessary step in determining appropriate work-rest regimens for static muscular work in industrial settings.