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Evaluation of spinal loading during lowering and lifting
Abstract
OBJECTIVE: To estimate the three-dimensional spinal loads during various lifting and lowering tasks. DESIGN: The in vivo measurements of the trunk dynamics, moments, and myoelectric activity were used as inputs into an electromyographic-assisted model used to predict the three-dimensional spinal loads. BACKGROUND: Previous studies of eccentric motions have investigated muscle activity, trunk strength, and trunk moments. A void in the body of knowledge exists in that none of these studies investigated spinal loading. METHODS: Ten subjects lifted (40 degrees of flexion to 0 degrees ) and lowered (0 degrees of flexion to 40 degrees ) boxes while positioned in a structure that restrained the pelvis and hips. The tasks were performed under isokinetic trunk velocities of 5, 10, 20, 40, and 80 deg s(-1) while holding a box with weights of 9.1, 18.2, and 27.3 kg. RESULTS: Lowering strength was found to be 56% greater than lifting strength. The lowering tasks produced significantly higher compression forces but lower anterior-posterior shear forces than the lifting tasks. The differences in the spinal loads produced by the two lifting tasks were attributed to differences in coactivity and unequal lifting moments (i.e. holding the box farther away from the body). CONCLUSIONS: The nature of the spinal loads that occur during lowering and lifting were significantly different. The difference in spinal loads may be explained by different lifting styles.
... From a thoracolumbar finite element (FE) model for lumbar posture, the maximum axial strain of the spine was estimated at 20% during stoop lifting tasks [49]. Also, the total predicted force on the LES was 242 N for a 45 • flexion bending of the hip [50]. ...
... Sensors 2023, 23, x FOR PEER REVIEW 6 of 19 estimated at 20% during stoop lifting tasks [49]. Also, the total predicted force on the LES was 242 N for a 45° flexion bending of the hip [50]. The mathematical modelling of a musculoskeletal system during lifting tasks can be intricate due to the numerous joints and muscles involved. ...
... Modelling of stoop lifting, utilizing a linked segment model of the human musculoskeletal system. Comparison of a developed mathematical model with experimental data on stoop lifting from[50]. The (left) figure shows the peak hip torque and lumbar torque during stoop lifting of various weights. ...
Work-related musculoskeletal disorders (WMSDs) are often caused by repetitive lifting, making them a significant concern in occupational health. Although wearable assist devices have become the norm for mitigating the risk of back pain, most spinal assist devices still possess a partially rigid structure that impacts the user’s comfort and flexibility. This paper addresses this issue by presenting a smart textile-actuated spine assistance robotic exosuit (SARE), which can conform to the back seamlessly without impeding the user’s movement and is incredibly lightweight. To detect strain on the spine and to control the smart textile automatically, a soft knitting sensor that utilizes fluid pressure as a sensing element is used. Based on the soft knitting hydraulic sensor, the robotic exosuit can also feature the ability of monitoring and rectifying human posture. The SARE is validated experimentally with human subjects (N = 4). Through wearing the SARE in stoop lifting, the peak electromyography (EMG) signals of the lumbar erector spinae are reduced by 22.8% ± 12 for lifting 5 kg weights and 27.1% ± 14 in empty-handed conditions. Moreover, the integrated EMG decreased by 34.7% ± 11.8 for lifting 5 kg weights and 36% ± 13.3 in empty-handed conditions. In summary, the artificial muscle wearable device represents an anatomical solution to reduce the risk of muscle strain, metabolic energy cost and back pain associated with repetitive lifting tasks.
... While physiological and psychosocial risk factors are indeed relevant to low back injury outcomes (Davis and Heaney 2000;Garg et al. 2014), many biomechanical investigations have focused on the interaction between joint compression force and repetition (Gallagher and Heberger 2013;Gooyers et al. 2015), with some including the additional element of loading variation (Zehr, Tennant, and Callaghan 2019;van Dieën et al. 2001) or joint posture (Gooyers et al. 2015;Marras et al. 1995;Marras et al. 1993). Compression forces experienced by lumbar spine joints during the performance of occupational lifting are considered sub-threshold, meaning they are less than existing estimates of ultimate compression tolerance (UCT) (Beach, Coke, and Callaghan 2006;Marras et al. 1997;Davis, Marras, and Waters 1998;Marras et al. 2006;Fathallah, Marras, and Parnianpour 1998). Therefore, resulting low back injuries have been attributed to a fatigue-failure mechanism (Gallagher and Schall Jr. 2017;McGill 1997;Marras 2000;Callaghan and McGill 2001b). ...
... The equations to characterize UCT responses were developed using a single normalized mean peak compression magnitude of 30% UCT. This normalized magnitude was intentionally selected to represent internal joint compression during a low-moderate demand occupational lifting tasks (Beach, Coke, and Callaghan 2006;Marras et al. 1997;Davis, Marras, and Waters 1998;Marras et al. 2006;Fathallah, Marras, and Parnianpour 1998). Although beyond the scope of the current study, future investigations may examine and validate the use of existing compression weighting factors to scale the UCT curves for a larger range of normalized compression forces (Parkinson and Callaghan 2007). ...
This study aimed to mathematically characterize the ultimate compression tolerance (UCT) as a function of spinal joint posture, loading variation, and loading duration. One hundred and fourteen porcine cervical spinal units were tested. Spinal units were randomly assigned to subthreshold cyclic loading groups that differed by joint posture (neutral, flexed), peak loading variation (10%, 20%, 40%), and loading duration (1000, 3000, 5000 cycles). After the assigned conditioning test, UCT testing was performed. Force and actuator position were sampled at 100 Hz. A three-dimensional relationship between UCT, loading variation, and loading duration was most accurately characterized by a second order polynomial surface (R 2 = 0.644, RMSE = 1.246 kN). However, distinct UCT responses were observed for flexed and neutral postures. A single second-order polynomial most accurately characterized the UCT-loading duration relationship (R 2 = 0.905, RMSE = 0.718 kN) for flexed postures. For neutral joint postures, separate second-order polynomial equations were developed to characterize the UCT-loading duration relationship for each variation group (R 2 = 0.618-0.906, RMSE = 0.617 kN-0.746 kN). These findings suggest that UCT responses are influenced by joint posture and these data may be used to inform ergonomic tools for the assessment of low back injury risk during occupational lifting. Relevance to human factors/ergonomics theory This study demonstrated that cyclic loading history can profoundly influence the time-varying response of the ultimate compression tolerance. This information should be considered in low back risk assessment tools where applied loads are normalized to estimates of ultimate compression tolerance.
... As examples, nurses and personal care attendants also frequently undertake manual handling tasks, and have high prevalence rates of low back pain [33][34][35][36]. Prior research by Davis, Marras [37] used similar box weights (ranging from 9.1 to 27.3 kg) however, their subjects performed their lifting and lowering tasks under isokinetic conditions where the velocity of movement was controlled. In our study subjects were free to move at a pace of their choice which we propose is more closely aligned with how typical tasks are completed. ...
Background:
Manual handling injuries amongst physiotherapists are common and the need to improve our understanding of causal influences is imperative.
Objective:
The objective was to determine whether intra-shift variations in manual handling task performance occurred in our cohort, which may inform mechanisms underpinning related injuries.
Methods:
We used motion capture, force plate dynamics and electromyography to identify variations in task performance, loading forces and muscle activity, during the performance of one static and one dynamic standardized manual handling task, pre- and post-shift, by 40 physiotherapists. Participants also rated their pain and fatigue on a visual analogue scale (VAS). Statistical analysis utilised paired samples Student's t tests.
Results:
Significant differences were seen in the EMG activity in the quadriceps during the static task only. No significant differences were seen for any of the kinematic variables. Significant differences in fatigue (p < 0.005) were seen between the pre- and post-shift sessions. Notably, there were significant differences in pain between the pre- and post-shift sessions in the static (p < 0.01) and dynamic tasks (p < 0.05). This increase in pain was at a level which impacted on function.
Conclusion:
Whilst significant variations in task performance were not observed, our findings indicate that physiotherapists frequently experience task-related pain towards the end of their shift. Contemporary research indicates that frequent transient low back pain may transition to a chronic disabling condition, as such we posit that the effects of intra-shift pain, and its causative factors, should be more widely considered in a 'whole-of-job' approach to mitigating risk in this demographic.
... The dependent variables fall into two main groups: 1) spine loading and 2) perceived exertion (RPE). The three-dimensional spine loading (lateral shear, anterior-posterior shear and compression) were predicted for each of the trials by the EMG-assisted model Davis et al. (1998);Fathallah et al. (1998); Granata and Marras (1995); Marras and Sommerich (1991). The prediction utilized an open loop model where an estimated muscle gain (based on closed-loop conditions) was applied to the muscle activity and trunk kinematics. ...
Transorting patients in beds and stretchers throughout hospitals is a significant manual handling concern for transport teams, nurses, and nursing aides. The objective of this study was to evaluate a power-drive intervention when pushing beds and stretchers with different weight patients. Twelve participants were part of a laboratory simulation where beds and stretchers were pushed down a straight away, around a corner, down a ramp, and up a ramp with and without utilization of the power-drive feature. Peak three-dimensional spine loads were estimated during the trials. In all, power-drive reduced the three-dimensional spine loads by 8%–21% as compared to the manual pushing of the beds and stretchers. Larger reductions were found for the tasks performed with the bed as opposed to the stretcher. The inexperience of the participants may have reduced the benefit of the power-drive as they appeared to not use it to the full extent. To minimize the loads being placed on healthcare providers’ spines and reduce the potential for injury hospitals should implement power-drive technologies on beds and stretchers.
... Indeed, there are several biomechanical models that describe how spinal muscles and passive tissues generate, at the L5-S1 joint, an extensor moment that grows proportionally with the trunk inclination and the weight of the payload (Chaffin, 1969;Toxiri et al., 2015;Koopman, 2020). Moreover, the greater the muscle activation, the higher the compression forces exerted on the lumbar disks (Dolan and Adams, 1993;Granata and Marras, 1995;Davis et al., 1998). If this compression exceeds specific biomechanical limits, the risk of developing MSDs increases (Moore and Garg, 1995). ...
Assistive strategies for occupational back-support exoskeletons have focused, mostly, on lifting tasks. However, in occupational scenarios, it is important to account not only for lifting but also for other activities. This can be done exploiting human activity recognition algorithms that can identify which task the user is performing and trigger the appropriate assistive strategy. We refer to this ability as exoskeleton versatility. To evaluate versatility, we propose to focus both on the ability of the device to reduce muscle activation (efficacy) and on its interaction with the user (dynamic fit). To this end, we performed an experimental study involving $ 10 $ healthy subjects replicating the working activities of a manufacturing plant. To compare versatile and non-versatile exoskeletons, our device, XoTrunk, was controlled with two different strategies. Correspondingly, we collected muscle activity, kinematic variables and users’ subjective feedbacks. Also, we evaluated the task recognition performance of the device. The results show that XoTrunk is capable of reducing muscle activation by up to $ 40\% $ in lifting and $ 30\% $ in carrying. However, the non-versatile control strategy hindered the users’ natural gait (e.g., $ -24\% $ reduction of hip flexion), which could potentially lower the exoskeleton acceptance. Detecting carrying activities and adapting the control strategy, resulted in a more natural gait (e.g., $ +9\% $ increase of hip flexion). The classifier analyzed in this work, showed promising performance (online accuracy > 91%). Finally, we conducted 9 hours of field testing, involving four users. Initial subjective feedbacks on the exoskeleton versatility, are presented at the end of this work.
Objective:
This study aimed to compare dynamic postural control between individuals with and without chronic low back pain (LBP) through load lifting and lowering.
Methods:
This cross-sectional study included 52 male patients with chronic LBP (age: 33.37 ± 9.23 years) and 20 healthy male individuals (age: 31.75 ± 7.43 years). The postural control parameters were measured using a force plate system. The participants were instructed to stand barefoot (hip-width apart) on the force plate and lift a box (10% of the weight of the participants) from the waist height to overhead and then lower it from overhead to waist height. The interaction between the groups and tasks was determined using a 2-way repeated-measures analysis of variance.
Results:
There was no significant interaction between the groups and tasks. Regardless of the groups, postural control parameters including amplitude (P = .001) and velocity (P < .001) in anterior-posterior (AP) direction, phase plane in medial-lateral (ML) direction (P = .001), phase plane in AP-ML direction (P = .001), and the mean total velocity (P < .001) were lesser during the lowering compared with lifting. The results indicated that, regardless of the tasks, the postural control parameters including velocity (P = .004) and phase plane in AP direction (P = .004), velocity in ML direction (P < .001), phase plane (AP-ML) (P = .028), and mean total velocity (P = .001) in LBP were lesser compared with the normal group.
Conclusion:
Different tasks affected postural control differently in patients with LBP and healthy individuals. Moreover, postural control was more challenged during the load-lowering than the load-lifting task. This may have been a result of a stiffening strategy. It may be that the load-lowering task might be considered as a more influential factor for the postural control strategy. These results may provide a novel understanding of selecting the rehabilitation programs for postural control disorders in patients.
Low-back disorders (LBDs) resulting in low-back pain (LBP) are common experiences in life. This chapter focuses on the preventive aspects of workplace design from an ergonomics standpoint. The science of ergonomics is concerned primarily with prevention. Many large and small companies have permanent ergonomic programs in place and have successfully controlled the risk as well as the costs associated with musculoskeletal disorders. While ergonomics typically addresses all aspects of musculoskeletal disorders as well as performance issues, the chapter aims to discuss issues and principles associated with the prevention of LBDs due to repetitive physical work. Numerous literature reviews have endeavored to identify specific risk factors that may increase the risk of LBDs in the workplace. There are numerous pathways to pain perception associated with LBDs. Quantitative video-based assessments have been used to better understand the association of LBP risk with workplace factors.
Modern approach towards biodegradable biomaterials involves significant capability of magnesium (Mg) alloys. Being a major constituent of the human body, Mg has extraordinary potential to facilitate as temporary orthopaedic implants. Despite many benefits within Mg and its alloys; such as excellent biocompatibility, biodegradability, satisfactory mechanical qualities, its use is still very limited. Rapid corrosion and hydrogen evolution are threats to its limited use. To estimate the mechanism and causes of corrosion in living environments for Mg-alloys accurately, in vitro study is necessary. The present review focuses on factors influencing corrosion rates (bio-corrosion) of Mg-alloys in vivo and in vitro studies. To understand the corrosion behaviour, factors like organic compounds, inorganic ions and some experimental process parameters taken into considerations and are analyzed. It is concluded that some of these factors affect the mechanism of corrosion greatly and their effective management is required to control their corrosion rates. Experimental conditions are most significant because they affect corrosion rates the most and can be helpful to stabilize it. The effects of these factors are summarized at the end of this review.
Lumbar spine injuries caused by repetitive lifting rank as the most prevalent workplace injury in the United States. While these injuries are caused by both symmetric and asymmetric lifting, asymmetric is often more damaging. Many back devices do not address asymmetry, so we present a new system called the Asymmetric Back Exosuit (ABX). The ABX addresses this important gap through unique design geometry and active cable-driven actuation. The suit allows the user to move in a wide range of lumbar trajectories while the “X” pattern cable routing allows variable assistance application for these trajectories. We also conducted a biomechanical analysis in OpenSim to map assistive cable force to effective lumbar torque assistance for a given trajectory, allowing for intuitive controller design in the lumbar joint space over the complex kinematic chain for varying lifting techniques. Human subject experiments illustrated that the ABX reduced lumbar erector spinae muscle activation during symmetric and asymmetric lifting by an average of 37.8% and 16.0%, respectively, compared to lifting without the exosuit. This result indicates the potential for our device to reduce lumbar injury risk.
A three-dimensional motion model has been developed that estimates loads on the lumbar spine under laboratory conditions that simulate manual materials handling conditions. Eleven subjects experienced spinal loading during an experiment in which conditions of trunk velocity, trunk torque output, and trunk asymmetric posture were varied in a series of isokinetic velocity trunk extensions. The electromyographic activity of 10 trunk muscles, subject anthropometry, and trunk kinetics were used as input to a biomechanical simulation model described in Part I of this study. The model calculated estimates of compression, shear, and torsion loading in the lumbar spine, as well as the torque production of the trunk, continuously throughout the exertion. Trunk torque estimates derived from this model were compared with measured trunk torque. The effects of trunk motion, posture, and torque level on spine loading as estimated by the model are discussed. It was concluded that this approach provides a straightforward means of assessing loading of the spine attributable to laboratory simulations of workplace conditions.
Traditionally most biomechanical models that are used to estimate the loading experienced by the spine during work focus on static, two-dimensional representations of the work. However, most work tasks impose loads on the lumbar spine under dynamic, three-dimensional conditions. The objective of this study was to describe the structure and logic of a model that is capable of producing estimates of spine loading under three-dimensional motion conditions. This model is intended for use primarily under laboratory conditions. The model was designed initially for workplace simulation in which the trunk is moving under symmetric and asymmetric constant velocity lifting conditions. Future embellishments may enable the model to be used under free dynamic conditions. The model predicts lumbar spine compression, shear, and torsional forces as well as trunk torque production continuously throughout the exertion. This information may be compared with spine tolerance limits so that the risk of causing a vertebral end-plate microfracture by workplace requirements could be determined.
An analysis was made of videotapes showing more than 2000 different box-handling tasks, performed by workers in nine factories. Sagittally symmetric lifting and lowering tasks were the exception rather than the rule, and there was a high incidence of body twisting as boxes were picked up and put down. Very few boxes had handles; even when handles were provided they were not always used. In the most common hand-hold position, one hand was at the upper-front corner of the box and the other was at the lower-rear corner. This position provided horizontal and vertical stabilization. During those parts of the task in which the subject supported the total weight of the box, this hand position accounted for almost half of the total number of hand positions used. The next most frequently used hand position appeared in fewer than 10% of the tasks. Hand positions were partially determined by subject, box, and task variables. The median box dimensions were 38.0 cm long, 30.5 cm wide, and 21.5 cm high. Median box weight was 9 kg. Most of the reaching occurred when the box was picked up and put down; the box was held relatively close to the body during the rest of the task.
There has been an abundance of evidence in the past decade that indicates that the asymmetric positioning as well as the dynamic action of the trunk during work greatly affects the ability of a worker to perform a lifting task. This is true because trunk strength decreases as the trunk moves more asymmetrically and more rapidly. Loading of the spine is also believed to increase under these conditions, since significantly greater trunk muscle activity has been observed under these conditions. Therefore, we must begin to document the asymmetric positions as well as the dynamic motion characteristics of the trunk when workers are exposed to various work tasks. This paper describes a lumbar motion monitor (LMM) that has been developed for this purpose. The LMM is an exoskeleton of the spine that is instrumented so that instantaneous changes in trunk position, velocity and acceleration can be obtained in three-dimensional space. The current study has assessed the accuracy and reliability of the LMM to measure such motion components. The results of this analysis indicate that the LMM is extremely reliable and very accurate. This study has shown that the LMM is about twice as accurate as a video-based motion evaluation system. The benefits and implications of using an LMM for work assessment and clinical use are discussed.
The purpose of this study was to determine the strength of trunk flexors and extensors in normal male subjects during isometric, concentric, and eccentric contractions. Subjects were tested in the sidelying position to minimize the effects of gravity. The pelvis and lower extremities were measured on a custom built force table (lowa Force Table). Muscle strength was expressed as a moment of force (external force times the moment arm) in Newton-meter (Nm) units. Greater Nm were registered in the muscle-lengthened position than in the muscle-shortened position for all isometric contractions. The Nm registered for eccentric contractions always exceeded the Nm registered for concentric contractions of the same muscle group. The Nm registered during contractions of trunk extensors always exceeded the values obtained during corresponding modes of contractions (isometric, eccentric, and concentric) of trunk flexors.J Orthop Sports Phys Ther 1980;1(3):165-170.
An experiment was performed to determine the reaction of the trunk muscles, using electromyography, and intra-abdominal pressure to components of trunk loading commonly seen in the workplace during manual materials handling. These components included angular trunk velocity, trunk position in three-dimensional space and trunk torque exertion level. The experiment was performed using 44 subjects. Subjects produced constant trunk extension torque about the lumbosacral junction while moving the trunk under constant angular velocity (isokinetic) conditions. Significant reactions to trunk angular velocity, trunk torque level, and unique combinations of trunk position and velocity were seen in all muscles of the trunk. The other components affected the muscles selectively according to function. Intra-abdominal pressure only reacted significantly to trunk angle and some unique trunk angle-asymmetry positions. The biomechanical implications of these findings are discussed. The reactions of the muscles to the various workplace components also were described quantitatively through equations that predict muscle activity levels.
Asymmetrical lifting and lowering are predominant activities in the workplace. Mechanical causes are suggested for many back injuries and the dynamic conditions within which spine loading occurs are related to spine loading increase. More data on tridimensional biomechanical lumbar spine loading during asymmetrical lifting and lowering are needed. A tridimensional dynamic multisegment model was developed to compute spinal loading for asymmetrical box-handling situations. The tridimensional positions of the anatomical markers were generated by a direct linear transformation algorithm adapted for the processing of data from two real and two virtual views (mirrors). Two force platforms measured the external forces. Five male subjects performed three variations (slow, fast and accelerated) of asymmetric lifting and two variations (slow and fast) of asymmetric lowering. The torsional, extension/flexion and lateral bending net muscular moments at the L5/S1 joint were computed and peak values selected for statistical analysis. For the lifting task, the fast and accelerated conditions showed significant increases over the slow condition for torsion, extension/flexion and lateral-bending moments. The accelerated condition also showed significant increases over the fast condition for extension. A comparison between lifting and lowering tasks showed equivalent loadings for torsion and extension. The moments were compared to average maximal values measured on equivalent male subject populations by isokinetic dynamometry. This showed torsional and extension values of 30 and 83% of the maximal possible subject capacity, respectively. These results demonstrated that dynamic factors do influence the load on the spine and highlighted the influence of both lifting and lowering on the loading of the spine. This suggested that for a more complete analysis of asymmetrical handling, the maximal velocity and acceleration produced during lifting should be included.