Shoulder-assist exoskeleton effects on balance and muscle activity during a block-laying task on a simulated mast climber

Abstract

Interest in utilizing exoskeletons to mitigate the risks of musculoskeletal disorders (MSDs) among construction workers is growing, spurred by encouraging results in other industries. However, it is crucial to carefully examine their impact on workers' stability and balance before implementation. In this study, seven male participants lifted a 35-lb cinder block from a production table to a simulated wall at two heights-elbow and shoulder levels-using three different exoskeleton models on an unstable platform, where their balance and shoulder muscle activity were assessed. Balance-related parameters, included mean distance (MDIST), total excursion (EXCUR), and mean velocity (VEL) of the center of pressure, were derived from force plate data. Muscle activity in six shoulder and upper arm muscles was estimated using electromyography (EMG) data. The results indicated that wearing two of the exoskeletons significantly increased both total and medio-lateral (ML) MDIST compared to not wearing an exoskeleton. Wearing one of the exoskeletons significantly increased total and ML VEL and ML EXCUR. Although lifting level did not have a significant impact on the balance parameters, it did affect the muscle activity in most of the measured muscles. Moreover, only one exoskeleton significantly reduced the activity in a particular shoulder muscle compared to no exoskeleton use. In conclusion, the evaluated shoulder-assist exoskeletons showed limited benefits for preventing upper extremity MSDs and may negatively affect whole-body balance during a block-laying task on an unstable platform. These findings underscore the importance of comprehensive evaluations of balance and effectiveness prior to adopting exoskeletons in construction.

Keywords: Construction; Masonry worker; Mast climber; Musculoskeletal disorders; Postural instability; Shoulder-assist exoskeletons; Whole-body balance.

Fig. 1.

(a) A customized workstation which simulates a typical working setup for masonry workers on an unstable mast climber work platform. (b) A close-up illustration of the unstable work platform.

Fig. 2.

(a) Three passive shoulder-assist exoskeletons tested in this study from left to right: Exo1, Exo2 and Exo3; (b) The simulated concrete block-laying activity of lifting a cinder block from the production table, turning, and placing it on the simulated wall (step 1 to step 3).

Fig. 3.

Placement of EMG electrodes on the subject’s dominant side, targeting six shoulder and upper arm muscles: upper trapezius, anterior deltoid, medial deltoid, posterior deltoid, biceps, and triceps.

Fig. 4.

Mean values and standard errors of balance-related parameters that were significantly affected by the exoskeleton device; MDIST-ML (a), MDIST (b), VEL-ML (c), VEL (d) and EXCUR-ML (e). Different letters denote values that are significantly different from one another.

Fig. 5.

The mean and standard error of EMG values (% of MaxD) that were significantly affected by exoskeleton device and/or the interaction between lifting height and exoskeleton device; PostDeltoid Mean (a), PostDeltoid Peak (b), MedDeltoid Mean (c), and UppTrapezius Mean (d). Different letters denote values that are significantly different from one another.