Influence of a passive lower-limb exoskeleton during simulated industrial work tasks on physical load, upper body posture, postural control and discomfort

Tessy Luger; Robert Seibt; Timothy J Cobb; Monika A Rieger; Benjamin Steinhilber

doi:10.1016/j.apergo.2019.05.018

Influence of a passive lower-limb exoskeleton during simulated industrial work tasks on physical load, upper body posture, postural control and discomfort

Appl Ergon. 2019 Oct:80:152-160. doi: 10.1016/j.apergo.2019.05.018. Epub 2019 May 30.

Authors

Tessy Luger¹, Robert Seibt², Timothy J Cobb², Monika A Rieger², Benjamin Steinhilber²

Affiliations

¹ Institute of Occupational and Social Medicine and Health Services Research, University Hospital Tübingen, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany. Electronic address: tessy.luger@med.uni-tuebingen.de.
² Institute of Occupational and Social Medicine and Health Services Research, University Hospital Tübingen, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.

PMID: 31280799
DOI: 10.1016/j.apergo.2019.05.018

Abstract

This study investigated the effect of wearing a passive lower-limb exoskeleton on physical load, kinematics, postural control, and discomfort. 45 healthy males participated and were exposed to three 21-min simulations, including screwing, cable-mounting, and clip-fitting. Each exposure comprised one of three exoskeleton statuses (standing, high and low sitting on exoskeleton) and three working distances (optimal, far, very far). The order of exoskeleton status and working distance were randomized across subjects. A force platform was used to calculate the mean center of pressure (COP) and absolute (SS_ABS) and relative static postural stability (SS_REL) as measures of postural control as well as the weight transferred to the exoskeleton supports as indicator of physical load. Neck and back angles were recorded together with electrical activity of four bilateral muscles (trapezius, erector, vastus, gastrocnemius). Discomfort was recorded before and after each exposure on an 11-point numeric rating scale. Physical load decreased due to the exoskeleton carrying up to 64% of the subject's body mass. The COP remained within the base of support with the lowest values of static postural stability for high sitting (27%). During sitting, vastus activity increased (∼95-135%) while gastrocnemius activity decreased (∼25%) compared to standing. Trapezius and erector activity levels showed only minor differences between exposures. Larger working distances resulted in a more anterior COP and increased erector activity. Standing without exoskeleton was related to less discomfort (0.5) than sitting on the exoskeleton (∼1.3). Working postures and distances changed SS_REL and activity levels of the vastus, gastrocnemius, and erector, but not SS_ABS. However, postural stability did not approach a critical state in our simulations without external perturbations. Therefore, investigating exoskeletons in the field will provide useful information about their effectiveness and usability in dynamic working situations where external forces could occur.

Keywords: Industrial ergonomics; Manual materials handling; Static postural stability.

Publication types

Clinical Trial

MeSH terms

Adult
Biomechanical Phenomena
Electromyography
Exoskeleton Device*
Healthy Volunteers
Humans
Lower Extremity
Male
Manufacturing and Industrial Facilities
Movement / physiology
Muscle, Skeletal / physiology
Postural Balance
Posture*
Task Performance and Analysis*
Torso / physiology
Weight-Bearing*
Work / physiology*