In-Field Training of a Passive Back Exoskeleton Changes the Biomechanics of Logistic Workers.

OCCUPATIONAL APPLICATIONSOccupational exoskeletons receive rising interest in industry as these devices diminish the biomechanical load during manual materials handling. Still, we have limited knowledge when it comes to in-field use. This gap often contributes to failure in the implementation of exoskeleton in industry. In this study, we investigated how a training protocol consisting of in-field use of a passive back exoskeleton affected the biomechanics of logistic workers. More specifically, we focused on how the variation of the muscular and kinematic patterns of the user was altered after exoskeleton training. We found that training had a positive effect on exoskeleton use, as a relative decrease of 6-9% in peak back muscle activity was observed post-training. Additionally, training decreased knee flexion by 6°-16°, indicating a more stoop lifting technique. The findings point at the potential benefits of applying a training approach when implementing a back-supporting exoskeleton in logistics.

Background: Occupational exoskeletons are an attractive solution to reduce the prevalence of attrition and work-related musculoskeletal disorders, such as low back pain, among manual workers. However, research has mostly focused on acute effects, while the effects of in-field use, and exoskeleton training are still to be addressed. Purpose: The aim of the present paper was to investigate how in-field use and exoskeleton training affected the biomechanics, acceptance, and comfort of logistic workers when using a passive back exoskeleton. Methods: Twenty workers were randomly distributed into control and intervention group. The tests consisted of standard lifting tasks with and without exoskeleton before and after a 5-week period. The intervention group underwent a 5-week progressive training protocol aiming at increasing the duration of use of the exoskeleton. The variation in muscle activity (surface electromyography) and full-body kinematics (IMU-based motion capture) were assessed during logistic work tasks. Additionally, acceptance, comfort, and perceived effort were collected. Compliance to the training protocol reached 74%. Results: Using the exoskeleton resulted in a 13­20% reduced variation in muscle activity of the back muscles across groups and lifting conditions including trunk extension. The changes in variation were driven by a decrease in peak muscle activity, which was further lowered by 6­9% after the 5-week training. Additionally, training induced decreased knee flexion indicating a more stoop lifting technique in the intervention group. Conclusions: The present results demonstrate that exoskeleton training optimized the human-exoskeleton interaction by deriving more effects of the exoskeleton ­ in this case by lowering the peak muscle activity of the user during manual materials handling. This underlines the importance of introducing training when implementing exoskeletons in industry. Additionally, the results indicate that a progressive implementation of back supporting exoskeletons in logistics can be beneficial in terms of lowering the biomechanical load during manual materials handling.

Biomechanical changes, acceptance, and usability of a passive shoulder exoskeleton in manual material handling. A field study.

Occupational exoskeletons contribute to diminish the biomechanical load during manual work. However, familiarization to the use of exoskeletons is rarely considered, which may lead to failure of acceptance and implementation. In this study, ten logistic workers underwent a 5-week progressive familiarization to a passive shoulder exoskeleton, while ten workers acted as controls. Tests pre and post the familiarization applied measurements of muscle activity and kinematics of back, neck, and shoulder, perceived effort, and usability-ratings of the exoskeleton. Exoskeleton use resulted in lower muscle activity of anterior deltoid (13-39%) and upper trapezius (16-60%) and reduced perceived effort. Additionally, it induced an offset in shoulder flexion and abduction during resting position (8-10°). No conclusions on familiarization could be drawn due to low adherence to the protocol. However, the emotions of the workers towards using the exoskeleton decreased making it questionable whether the shoulder exoskeleton is suitable for use in the logistics sector.

The effects of unstable surface conditions on lower limb biomechanical parameters during running.

The aim of this study was to analyse the kinematics and kinetics of the lower extremities in the sagittal plane, when running under unstable surface conditions. It was hypothesized that 1) a greater effect of the unstable surface would occur in the gastrocnemius, soleus, and tibialis anterior muscles, contributing to plantar- and dorsi-flexion, compared to muscles involved in hip and knee movements, and 2) the step-to-step absolute variability would be larger in the unstable condition. Eleven male-subjects completed running trials on stable and unstable surfaces in a laboratory setup. Inverse kinematic and dynamic analyses were conducted to calculate kinematics and moments at the lower extremity joints. Additionally, muscle force and activation related variables were calculated for six lower limb muscles using musculoskeletal modelling. Furthermore, the individual SD was calculated for all the variables as a measurement of absolute step-to-step variability. The unstable surface led to a decrease in joint ROM of the knee and ankle by 8.3% and 11.4%, and a decrease of 13.3% on average in force development of the ankle plantar-flexor, which also was reflected by decreasing muscle peak forces of Soleus and Gastrocnemius of 10.3% and 10.8%. Furthermore, an increase of force of Biceps Femoris and activation of Vastus Lateralis were found during the unstable condition. The step-to-step variability increased up to 158% when changing to the unstable condition. In conclusion, the findings revealed for the first time, lower ankle muscle forces mostly reflecting biomechanical adjustments to the surface conditions as well as larger absolute variability when running on the unstable surface.