DOI: 10.5061/dryad.fbg79cp45
title: Bilateral back extensor exosuit (BBEX) for multidimensional force assistance and prevention of spinal overuse injuries during lifting

description: Lumbar spine injuries resulting from heavy or repetitive lifting remain a
 prevalent concern in workplaces. Back-support devices have been developed
 to mitigate these injuries by aiding workers during lifting tasks.
 However, existing devices often fall short in providing multidimensional
 force assistance for asymmetric lifting - an essential feature for
 practical workplace use. Additionally, validation of device safety across
 the entire human spine has been lacking. This paper introduces the
 Bilateral Back Extensors Exosuit (BBEX), a robotic back-support device
 designed to address both functionality and safety concerns. The design of
 the BBEX draws inspiration from the anatomical characteristics of the
 human spine and back extensor muscles. Employing a multi-degree-of-freedom
 architecture and serially connected linear actuators, the device's
 components are strategically arranged to closely mimic the biomechanics of
 the human spine and back extensor muscles. To establish the efficacy and
 safety of the BBEX, a series of human-subject experiments were conducted.
 Eleven healthy male participants engaged in symmetric and asymmetric
 lifting tasks while wearing the BBEX. The results confirm the ability of
 the BBEX to preserve the natural range of motion of the back and to
 provide effective multidimensional force assistance. Moreover,
 comprehensive safety validation was achieved through analyses of muscle
 fatigue in the upper and the lower erector spinae muscles, as well as
 mechanical loading on spinal joints during both lifting scenarios. By
 seamlessly integrating functionality inspired by human biomechanics with a
 focus on safety, this study offers a promising solution to address the
 persistent challenge of preventing lumbar spine injuries in demanding work
 environments.
description: Eleven men who had no histories of low back injury or
 musculoskeletal disorders volunteered to participate in the study. The
 mean (SD in parenthesis) of age, height, sitting height and body mass of
 the participants were 25.73 years (0.96 years), 174.45 cm (3.06 cm), 89.91
 cm (2.57 cm) and 76.36 kg (8.41 kg), respectively. Further details on the
 participants are described in table S2. All participants received an
 information letter prior to the experiments and signed an informed consent
 form. All participants performed two types of tasks: a
 symmetric lifting task and an asymmetric lifting task, and conducted each
 task twice, with and without the BBEX. Thus, a total of four experiments
 were conducted for each participant. Each experiment was performed at
 intervals of one week to exclude the effects of the previous experiment.
 All experimental procedures performed in the study were approved by the
 Institutional Review Board of Seoul National University (IRB No.
 1912/001-003), and all participants were familiarized with the
 experimental procedures and the BBEX prior to the experiments. In the
 preparation process, EMG electrodes and reflective markers were attached
 to the participants, and a heart rate monitor armband was placed on their
 right upper arm. For the experiments with the device, the BBEX was fitted
 and adjusted to the individual participants. Subsequently, reflective
 markers were attached to the suit as well. After the preparation, the
 participants took a five-minute break (58) to relieve any fatigue that
 might occur during the preparation process. The participants lowered and
 lifted a weight of 5.5 kg 30 times with an interval of 8 seconds for each
 experiment. In the symmetric lifting task, the participants performed the
 cyclic lifting task in the sagittal plane to touch a pad in front of the
 foot. In the asymmetric lifting task, the participants performed the
 lifting by rotating the trunk alternately left and right side to touch a
 pad, which was located +-45 degrees to the sagittal plane. We provided
 auditory feedback using a metronome to control lifting speed, and the
 participants were asked to handle the weight at a constant speed as
 smoothly as possible. The weight and the lifting interval were chosen to
 follow the limits suggested by the National Institute for Occupational
 Safety and Health Guidelines while guaranteeing 30 continuous lifts (59).
 Since the lower back extensor muscles become silent in the upright
 posture, we limited the maximum range of extension during the
 upward-lifting phase to induce sustained muscle contraction. To prevent
 the involvement of the lower extremities, participants were asked not to
 bend their knees and were instructed to keep the weight within the marked
 area on the floor. The ground level of the floor on which the individual
 participants put their feet was adjusted using a platform in consideration
 of the participants' range of motion (see Movie S7 for the experiment
 description).
description: # Bilateral Back Extensor Exosuit (BBEX) for Multidimensional Force
 Assistance and Prevention of Spinal Overuse Injuries during Lifting
 [https://doi.org/10.5061/dryad.fbg79cp45](https://doi.org/10.5061/dryad.fbg79cp45) //////////////////////////////////////////////////////////////////////////////////////// DATA AND ANALYSIS CODE FOR: Bilateral Back Extensor Exosuit (BBEX) for Multidimensional Force Assistance and Prevention of Spinal Overuse Injuries during Lifting //////////////////////////////////////////////////////////////////////////////////////// 'Suit' refers to the condition where participants conducted the experiment wearing the BBEX. 'Nosuit' refers to the condition where participants conducted the experiment without the BBEX. 'Sagittal' and 'Symmetric' refer to the experiments where participants conducted lifting tasks symmetrically in a sagittal plane. 'Side' and 'Asymmetric' refer to the experiments where participants conducted lifting tasks asymmetrically. ## **CONTENT** Folders 1\. BBEX_OpenSim: Data and setup files for musculoskeletal analysis using OpenSim 2\. EMG 3\. HR, RPE ## 1. BBEX\_OpenSim: Data and setup files for musculoskeletal analysis using OpenSim *.trc files * Time: seconds * X, Y, Z: mm * Please see provided link for further information about  .trc file format (https://opensimconfluence.atlassian.net/wiki/spaces/OpenSim/pages/53089972/Marker+.trc+Files) * .trc files can be opened via excel, OpenSim, VScode *_external.txt files * External forces provided by BBEX * Format \[1st_Module_Left_Force_Vector, 1st_Module_Left_Force_Position, Foot_Left_Force_Vector, Foot_Left_Force_Position, 1st_Module_Right_Force_Vector, 1st_Module_Right_Force_Position, Foot_Right_Force_Vector, Foot_Right_Force_Position, 4th_Module_Left_Force_Vector, 4th_Module_Left_Force_Position, 4th_Module_Right_Force_Vector, 4th_Module_Right_Force_Position, 2nd_Module_Force_Vector, 2nd_Module_Force_Position, 3rd_Module_Force_Vector, 3rd_Module_Force_Position] * *Force_Vector = [Fx, Fy, Fz] : N * *Force_Position = [Px, Py, Pz] : mm *.osim files * ``` OpenSim model file corresponding to each participant ``` * Please see provided link for further information about .osim file and opensim (https://opensimconfluence.atlassian.net/wiki/spaces/OpenSim/pages/53088700/Tutorial+1+-+Intro+to+Musculoskeletal+Modeling) * .osim files can be opened via OpenSim *.xml files * ``` Setting files for inverse kinematics, and inverse dynamics ``` * .xml files can be opened via VScode *_External3.xml files * ``` Setting files for External Loads ``` * Please see provided link for further information about External loads and Inverse Dynamics (https://opensimconfluence.atlassian.net/wiki/spaces/OpenSim/pages/53090053/How+to+Use+the+Inverse+Dynamics+Tool) *_External3.mot files * ``` Files containing External Loads according to time ``` * Time: seconds * *Force_Vector = [Fx, Fy, Fz] : N * *Force_Position = [Px, Py, Pz] : mm * .mot files can be opened via excel, OpenSim, VScode JR_Raw.xlsx files * Sheet1: Results table of peak joint reaction forces (unit: N) * 'Subject' Column: Subject Number * 'Suit' Column: * 0 = Experiment conducted without wearing BBEX * 1=  Experiment conducted with wearing BBEX * 'Exp' Column: * 0 = Symmetric Lifting Task * 1=  Asymmetric Lifting Task * 'Time' Column: * 1= Initial Stage * 2= Middle Stage * 3= Final Stage IK_Raw.xlsx files * Sheet1: Results table of peak joint angles (unit: degree) * 'Subject' Column: Subject Number * 'Suit' Column: * 0 = Experiment conducted without wearing BBEX * 1=  Experiment conducted with wearing BBEX * 'Exp' Column: * 0 = Symmetric Lifting Task * 1=  Asymmetric Lifting Task * 'Time' Column: * 1= Initial Stage * 2= Middle Stage * 3= Final Stage BBEX_InverseKinematics_Statistics_ANOVA_PWC_R.R files * Sample R Code for statistical analysis ## 2. EMG Unit * Time: seconds * EMG: mV EMG_MDF_Raw.xlsx files * Sheet1: Results table of Median Frequency of EMG * 'Subject' Column: Subject Number * 'Suit' Column: * 0 = Experiment conducted without wearing BBEX * 1=  Experiment conducted with wearing BBEX * 'Exp' Column: * 0 = Symmetric Lifting Task * 1=  Asymmetric Lifting Task * 'Time' Column: * 1= Initial Stage * 2= Middle Stage * 3= Final Stage ## 3. HR\_RPE HRR_RPE_Raw.xlsx files * Sheet1: Results table of HRR (Unit: %) and RPE (Unit: Borg Scale 6-20) * 'Subject' Column: Subject Number * 'Suit' Column: * 0 = Experiment conducted without wearing BBEX * 1=  Experiment conducted with wearing BBEX * 'Exp' Column: * 0 = Symmetric Lifting Task * 1=  Asymmetric Lifting Task * 'Time' Column: * 1= Initial Stage * 2= Middle Stage * 3= Final Stage Heart Rate_final.xlsx files * HR: Raw data of measured Heart Rate (HR) * HRR: Heart Rate Reserve (HRR) calculated using HR * HRR_final: Final results of HRR with outlier participants data filtered out and summarized as initial, middle, and final stages RPE_final.xlsx files * RPE: Raw data of measured Rating of Percieved Exertion (RPE) * RPE_filtered: Results of RPE with outlier participants data filtered * RPE_final: Final results of RPE summarized as initial, middle, and final stages