Abstract
Background: Workplace adaptation is the preferred method of intervention to diminish risk factors associated with the development of work-related shoulder disorders. However, the majority of the workplace assessments performed are subjective (e.g., questionnaires). Quantitative assessments are required to support workplace adaptations. The aims of this study are to assess the concurrent validity of inertial measurement units (IMUs; MVN, Xsens) in comparison to a motion capture system (Vicon) during lifting tasks, and establish the discriminative validity of a wireless electromyography (EMG) system for the evaluation of muscle activity. Methods: Sixteen participants performed 12 simple tasks (shoulder flexion, abduction, scaption) and 16 complex lifting tasks (lifting crates of different weights at different heights). A Delsys Trigno EMG system was used to record anterior and middle deltoids’ EMG activity, while the Xsens and Vicon simultaneously recorded shoulder kinematics. Results: For IMUs, correlation coefficients were high (simple task: >0.968; complex task: >0.84) and RMSEs were low (simple task: <6.72°; complex task: <11.5°). For EMG, a significant effect of weight, height and a weight x height interaction (anterior: p < 0.001; middle: p < 0.03) were observed for RMS EMG activity. Conclusions: These results suggest that wireless EMG and IMUs are valid units that can be used to measure physical demand in workplace assessments.
Highlights
Work-related upper extremity disorders represent a major and increasingly prevalent health problem in industrialized countries [1], as they incur important economic costs, lead to loss of productivity, affect workers’ quality of life and can lead to premature retirement [2]
Simple shoulder movements without combined trunk motion showed the lowest root-mean-square error (RMSE) and average error of estimate (RMSE = 2.8–6.7◦ ; error of estimate= 2.4–5.5◦ ), while more variability was present for combined trunk movement, for trunk rotation and lateral bending
The comparison between Xsens and Vicon shows that inertial measurement units (IMUs) are valid to assess shoulder elevation range of motion (ROM) during simple arm movements (r ≥ 0.917; RMSE ≤ 12.82◦ ; average error of estimate ≤ 10.15◦ ) and complex lifting tasks, regardless of the height at which the crates are placed on the shelves of Valpar 19 (r ≥ 0.839; RMSE ≤ 12.68◦, average error of estimate ≤ 10.24◦ )
Summary
Work-related upper extremity disorders represent a major and increasingly prevalent health problem in industrialized countries [1], as they incur important economic costs, lead to loss of productivity, affect workers’ quality of life and can lead to premature retirement [2]. The shoulder is the joint most frequently affected by work-related upper extremity disorders, with a prevalence varying between 18 and 26% [3,4]. Of arm elevation) and tasks requiring significant force (e.g., more than 10% of the maximal voluntary contraction, or lifting objects weighing more than 20 kg) appear to be important risk factors in the development of work-related shoulder disorders [5,6,7]. To prevent work-related shoulder disorders, most interventions use workplace adaptations or educational programs to decrease the physical demands on the shoulder joint. Workplace adaptation is the preferred method of intervention to diminish risk factors associated with the development of work-related shoulder disorders. The majority of the workplace assessments performed are subjective (e.g., questionnaires). Results: For IMUs, correlation coefficients were high
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