Occupational Exoskeletons: Overview of Their Benefits and Limitations in Preventing Work-Related Musculoskeletal Disorders

OCCUPATIONAL APPLICATIONS There is a growing interest in industry toward the use of occupational exoskeletons, with claimed efficiency in reducing physical demands at work. In this paper, we review existing evidence regarding the benefits and risks of using these technologies to attenuate the injury mechanisms for occupational musculoskeletal disorders (MSDs). More specifically, we focus on the underlying mechanisms of low back pain and shoulder tendinopathies, since these are the conditions targeted by the current use of exoskeletons for occupational application. While the potential for occupational exoskeletons to attenuate muscular demand in the back or upper limbs appears fairly promising, we conclude that the current state of knowledge does not allow for an unreserved endorsement of the use of these technologies for the prevention of MSDs. Unwanted consequences of using exoskeletons during handling tasks are also discussed here, such as postural strains and modified kinematics. Several gaps in current knowledge are also highlighted, notably related to the impacts of physical assistance on neuromuscular coordination and joint movements, the occurrence of muscle fatigue, and chronic physiological adaptations. TECHNICAL ABSTRACT Background: To address the prevalence of work-related MSDs in physically demanding tasks, research is now focusing on new approaches, such as the use of exoskeletons. Purpose: Based on the available evidence underlying the claimed efficiency of occupational exoskeletons in reducing biomechanical strains at work, the aim of this paper is to relate the claimed effectiveness of exoskeletons at reducing muscle demand to the pathophysiological mechanisms underlying MSDs. A further aim is to analyze the literature to highlight the main deficiencies in current knowledge, in order to guide the research necessary to develop future generations of exoskeletons. Methods: A narrative review was completed, based on an electronic literature search, considering occupational applications of exoskeletons from January 1980 to January 2019. Results: Thirty articles, each of which evaluated the effects of occupational exoskeletons on physical workload, were considered relevant to discuss with respect to the pathophysiological origins of MSDs. We found 22 studies that were directly related to back-assistive exoskeletons. Studies mainly focused on back muscle activity, but additional factors contributing to low back pain were also considered (muscle fatigue, spine loading, perceived pain, and posture). Eight papers were directly related to upper-limb exoskeletons. Conclusions: Within the scope of the specific task for which exoskeleton use has been designed, exoskeletons have been found to have clear potential in limiting local muscular demands. However, the current state of knowledge does not support an unreserved endorsement for using these technologies for MSDs prevention. Additional research is needed to better understand posture and movement control mechanisms, when the postural and/or upper limb muscular chains are assisted. The impacts of movement assistance on neuromuscular coordination and joints kinematics also need to be clarified. Several other questions remain to be examined, in particular related to the occurrence of muscle fatigue and chronic adaptations.