Changes in Neuromuscular Activity with the Use of an uPper Limb Exoskeleton: the ELMA Prototype. Preliminary Results

Weightlifting is one of the most common activities in the occupational field (e.g., industrial, logistics, manufacturing, construction), and an important source of risk to the health and safety of workers. Nowadays, the creation and progressive introduction of industrial exoskeletons aim to increase the performance of a worker, and to provide a solution to prevent the most prevalent musculoskeletal disorders (i.e., in lower back and upper extremities). The ELMA project (Exoskeleton for Load Manipulation Assistance) is currently designing an exoskeleton to assist the upper limbs of workers (i.e., Shoulder and elbow joints), to alleviate muscle load during the lifting and movement of different charges. The objective of this study was to determine the effectiveness of the ELMA exoskeleton prototype in improving the upper limb neuromuscular activity during elbow flexion, without compromising back and neck muscle activity. Eight healthy volunteers (age: 26.5 ± 2.98 years), participated in the study. During the session test we registered the surface electromyography of 8 muscles of the upper limb, trunk, and neck during unilateral (3.25 kg load), and bilateral (6.5 kg load) lifting tasks performed with and without the assistance of the ELMA exoskeleton prototype. Although the data obtained did not show significant differences in any of the comparisons, it was observed large, and medium to large effect size in numerous comparisons. It seems that the use of ELMA assisted the elbow flexion lifting the charge, producing a lower muscle activity of the brachioradialis, and biceps brachii. Moreover, the back muscles (i.e., lumbar and dorsal erector spinae, and quadratus lumborum) seem to show a lower neuromuscular activation with the use of the ELMA exoskeleton. However, it seems that a higher activation of the upper trapezius muscle could occur with the use of the device. Future studies must resolve these problems and improve the final ELMA design.