Evaluation of a Lower Leg Support Exoskeleton on Floor and Below Hip Height Panel Work

Abstract

Objective The aim of this study is to determine the effectiveness of using a leg support exoskeleton (legX) in different modes on simulated work tasks which emulate real-world job tasks. Background Prolonged kneeling and squatting tasks increase the risk of work-related musculoskeletal disorders at the knee in industrial occupations. Methods We evaluated legX capable of spring assistance throughout one’s range of motion and/or locking support at a fixed angular position. Participants performed a dynamic panel task, alternating between hip and knee height, and a sustained floor level task with and without the exoskeleton. The exoskeleton was evaluated in spring mode, locking mode, and spring + locking mode for the panel task and only in locking mode for the floor task. The participants’ ( N = 15) muscle activity was recorded for the right lumbar erector spinae, thoracic erector spinae, tibialis anterior, rectus femoris, semitendinosus, and lateral gastrocnemius. Results Significant reduction of the rectus femoris activity was observed with the exoskeleton (median reduction: 22%–56% and peak reduction: 12%–48% for the panel task and median reduction: 57% and peak reduction:34% during the floor task). Conclusion legX significantly reduces rectus femoris activity during squatted static (floor) and dynamic (panel) work and may reduce pain and discomfort associated with squatting and potentially reduce the risk of developing knee disorders. Dynamic tasks benefit from both locking modes and spring assistance, the greatest benefit occurring with a combination of the two. Application These results show that the legX can be beneficial to activities such as electrical panel work, grinding, sanding of larger surfaces, and concrete laying.

Guidelines for Working Heights of the Lower-Limb Exoskeleton (CEX) Based on Ergonomic Evaluations

“…The TeleMyo 2400 DTS System (Noraxon, AZ, USA) was used to evaluate the effects of independent variables on all 16 muscle groups examined in this study. The upper trapezius (UT), erector spinae (ES), middle deltoid (MD), triceps brachii (TB), biceps brachii (BB), biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA) muscles on the left and right side of the body were chosen based on previous studies showing significant changes in the activity of these muscles with use of an exoskeleton [ 21 , 23 , 24 , 26 , 27 ]. Surface electrodes were positioned over the bellies of those muscles, parallel to the longitudinal axis of the muscle fibers, as recommended by Zipp [ 34 ] ( Figure 4 ).…”

“…Wearable exoskeletons are actively used in various fields, such as in military and industrial settings, as components of rehabilitation assistance, and on automobile assembly lines because the exoskeletons do not require separate spaces [ 17 ]. Usability evaluation studies have been conducted using EMG [ 4 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], body posture angle [ 26 ], heart rate [ 28 ], subjective discomfort rating [ 20 , 21 , 23 , 24 , 25 , 29 ], and performance [ 24 , 29 ] at actual industrial sites or in various laboratory environments.…”

“…Pillai et al [ 27 ] tested the effects of wearing another passive lower-limb exoskeleton, the LegX, on the activities of the LES (lumbar erector spinae), TES (thoracic erector spinae), TA (tibialis anterior), RF (rectus femoris), ST (semitendinosus), and GAS (lateral gastrocnemius) muscles during drilling tasks at hip and knee height. They found a significant reduction in RF activity only (12–48%) when the exoskeleton was used.…”

A Semi-active Exoskeleton Based on EMGs Reduces Muscle Fatigue When Squatting

“…A (quasi) passive exoskeleton was driven by any type of actuator, but rather applied elastic materials, springs or dampers to store energy harvested by human motion and to use this as required to support a posture or a motion (De Looze et al, 2016). LegX (6.2 kg) (Pillai et al, 2020) and the Chairless Chair (Spada et al, 2018) were passive exoskeletons, which were used to reduce the effort of muscles when the wearer was in a position (e.g., squatting and semisquatting) and they wished to maintain the position for a long time. But the chairless chair required wearers to fix a position by crouching down into the required position and pushing a button.…”

Introduction to the Human Factors Special Issue on User-Centered Design for Exoskeleton

“…Two studies investigated the biomechanical responses in the lower back when wearing exos (Alemi et al, 2020;Madinei et al, 2020). Three studies investigated the impact of lower extremity exos during various manual handling tasks (Bequette et al, 2020;Kermavnar et al, 2020;Pillai et al, 2020). Together, these studies provide some insight into the complex relationship between the exo and the human musculoskeletal system.…”