Temporal effect of construction workforce physical strain on diminishing marginal productivity at the task level

Physiological status and environmental stressors are known to influence workforce performance at the individual worker level. A previous study, which conducted a cross-sectional comparison in repetitive material-handling construction activities, suggested that a U-shaped relationship existed between physical strain and productivity at the group level. This research revisits those findings to further investigate the U-curve relationship between physical strain and productivity at the group level and validate the concept of diminishing marginal productivity. Heart rates were measured as an indicator of subjects' physical strain, whereas task productivity was estimated by work sampling. Eighty person-hour data were converted into panel data sets by dividing each subject's 4-h experimental data into 5-min intervals. These data sets were subsequently used to evaluate the effects of time on physical strain and productivity with 5-min lags. The study found a U-curve relationship between physical strain and task-level productivity at the group level while controlling for individual characteristics. The U-shape relationship was constant in the low-performance and high-performance groups, although the degrees of the polynomials differed. Productive workers will remain more productive than low-productive workers with increased physical strain.