Investigation on a Developed Wearable Assistive Device (Wad) in Reduction Lumbar Muscles Activity

Abstract

A new wearable assistive device (WAD) was developed to decrease required force on the lumbar spine in static holding tasks. In order to obtain moments on lumbar spine in two conditions, with and without WAD, a biomechanical static model was used for estimation of external moments on lumbar spine. The results of biomechanical models indicated that there was a reduction in the lumbar moment ranging from 20% to 43% using WAD depending on the load and flexion angle. A total of 15 male healthy subjects were tested to experimentally verify the predicted reduction of external moments on the spine by wearing WAD. Normalized electromyography (EMG) of the right and left lumbar and thoracic erector spinae (LES, TES), latissimus dorsi (LD), external oblique (EO), internal oblique (IO) and rectus abdominus (RA) muscles were monitored at three lumbar flexion positions (0°, 30° and 60°) in symmetric posture with three different loads (0, 5 and 15 kg) in two conditions of with and without WAD. The effects of WAD and load were significant for all muscles but the interaction effects were only significant for extensor muscles groups (p < 0.016). Results of statistical analysis (ANOVA) on the normalized EMG while wearing WAD indicated that the muscle activity of right and left LES, TES and LD muscles significantly decreased (p < 0.001). This reduction for right LES, TES, LD muscles at 15 kg load and 60° trunk flexion were 23.2%, 30% and 27.8%, respectively which were in good agreement with the biomechanical model results.

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

“…Pillai et al [ 27 ] reported a 12–48% reduction in RF muscle activity in a drilling task with use of a lower-limb exoskeleton. Other upper-limb exoskeleton studies also showed a 49–62% [ 23 ], 36–56% [ 20 ], 17–23% [ 4 ], and 20–44% [ 21 ] reduction in upper body muscle activities with use of the upper-limb exoskeleton.…”

“…The risk of musculoskeletal disorders in the agricultural sector is higher than in other sectors [ 4 , 5 ]. Awkward working postures occur for more than 50% of daily working hours during agricultural work [ 6 , 7 ].…”

“…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.…”

“…In a laboratory environment, Bosch et al [ 21 ] reported that subjective discomfort and muscle activities of the lumbar muscle (ES), trapezius (TR), and biceps femoris (BF) were reduced by about 20–44% during a simulated assembly task and static holding task when the participants wore an upper-limb Laevo exoskeleton. Heydari et al [ 4 ] also reported a 17–23% reduction in activation in the lower back muscles (ES, LD: latissimus dorsi; EO: external oblique; IO: internal oblique), but no change in the abdominal rectus abdominis (RA) muscles, during a static holding task when participants used a personal lifting assistive device (PLAD) and wearable assistive device (WAD). Another static holding task study of a passive arm exoskeleton showed decreases in the activities of the biceps brachii (BB), medial deltoid (MD), erector spinae (ES), rectus abdominis (RA), biceps femoris (BF), rectus femoris (RF), tibialis anterior (TA), and gastrocnemius (GAS) muscles when participants wore the exoskeleton, which corresponded to a decrease in local discomfort [ 23 ].…”

Back-Support Exoskeletons for Occupational Use: An Overview of Technological Advances and Trends

“…Similar use of integrated gas springs is found on the Laevo (Laevo, 2017) and BackX (SuitX, 2017). Elastic bands are used on a number of devices, including the Personal Lift Augmentation Device (PLAD) (Abdoli-E, Agnew, & Stevenson, 2006), Smart Suit Lite (SSL) (Imamura, Tanaka, Suzuki, Takizawa, & Yamanaka, 2011), Wearable Assistive Device (WAD) (Heydari, Hoviattalab, Azghani, Ramezanzadehkoldeh, & Parnianpour, 2013), and biomechanically assistive (B.A.) garment (Lamers, Yang, & Zelik, 2017).…”