Recent advancements in wearable health devices equipped with biosensor systems (e.g., heart rate (HR) sensor) have provided an ample opportunity to continuously measure and understand workers' physical demands from construction work. Specifically, a relative measurement of physical demands, which is a percentage of HR reserve (%HRR), is convenient and useful by normalizing individual differences of HR. Since affordable HR monitoring using wearable devices (particularly, a comfortable wristband-type device: wristband hereafter) becomes available, %HRR-based physical demand measurement, which can be continuously calculated without interfering with workers' ongoing work, provides an enormous potential to protect workers' safety and health and to sustain expected productivity. This research investigates the usefulness of affordable %HRR-based physical demand measurement using a wristband from a case study of 19 workers in construction sites. The aim of the analysis is to examine the potential of this continuous measurement in capturing any significant physical demand variations, by investigating in-depth information on factors affecting physical demands (e.g., work tasks, individual and environmental factors). The results show that workers' physical demands are highly variable according to their working patterns (i.e., direct work, and indirect work including tool/equipment/ material handling, traveling, and preparatory work), combined influences of work tasks, as well as individual and environmental factors (e.g., age and heat stress). These results demonstrate the need for continuous physical measurement during workers' ongoing work so that any significant high physical demands, which need to be avoided if possible, can be captured. The findings of this paper show that the continuous measurement of physical demands using a wristband provides rich information to understand, manage, and design physically demanding construction work (e.g., flexible work-rest cycle and managing demanding indirect work) by balancing workloads throughout a day and/or reducing unnecessary physical demands beyond direct work. By anticipating potential health and safety problems from excessive physical demands, as well as productivity loss before they occur, this research will have an ameliorative impact across the construction industry.
