Influence of Panelized Wall Mass and Wall Erection Tasks on Physical Demands in Residential Construction: Muscle Activity and Trunk Kinematics

摘要

One trend in the residential construction industry is a move towards more industrialized methods, such as panelized (prefabricated) walls. As a consequence, construction workers may have higher levels of physical exposures due to the large mass of panelized walls and incidental changes in the process of wall erection. The purpose of this study was to investigate trunk kinematics and muscle activities associated with different wall masses and wall erecting tasks. Seventeen healthy participants performed eight different wall erection tasks (2 lifting (L), 4 erecting (E), 1 carrying (C), and 1 moving (M)) simulating observations from the field. Two 243.8 x 304.8 cm panelized walls were used, with masses of 53.6 kg (unsheathed) and 107.8 kg (sheathed). Trunk kinematics were measured using a passive marker system. Surface electromyographic (EMG) responses of eight trunk muscles were recorded bilaterally. All EMG responses were pre-processed (root mean square (RMS) converted and filtered) then normalized (nEMG) to peak values recorded during maximum voluntary contractions (MVCs). Peak trunk angles (relative to the pelvis) as well as mean and 90th percentile nEMG responses during each task were calculated, and subject to multivariate and univariate analyses of variance (MANOVAs and ANOVAs) to detect the overall effects of wall mass and erection task. Multivariate effects of wall mass, wall erection task and their interaction were significant. Univariate effects of task and task×mass were significant on most of the 90th percentile nEMG and peak trunk angles. In contrast, the effect of wall mass was significant only for peak trunk angles. Overall, the tasks of carrying and lifting from the ground required higher muscle activities. The largest 90th percentile nEMG (61% MVC) was found in the left longissimus thoracis pars lumborum during the carrying task. Of note, higher levels of activities in 10 muscles were observed with the unsheathed wall during erecting from the ground. Handling the sheathed wall significantly increased peak trunk angles during erecting tasks from knuckle height, and the largest peak trunk angle (88 o) was found in the sagittal plane during lifting from the ground. These results suggest that sheathed walls and certain tasks involved in wall erection process may expose construction workers to both high levels of muscle activities (and likely high spinal loads) as well as highly non-neutral trunk postures. Understanding trunk kinematics and muscle activities during different wall erection tasks is expected to be beneficial for quantifying the risks associated with these tasks under a variety of panel design alternatives.