Spine loading and trunk kinematics during team lifting (original) (raw)
Related papers
Gender influences on spine loads during complex lifting
The Spine Journal, 2003
Background context: Previous research has documented differences in spine loading between genders when the imposed load is normalized relative to the size of the person. However, under realistic work conditions the magnitude of the load handled is seldom adjusted relative to worker anthropometry. Thus, there is a void in our knowledge in that we do not understand how material handling influences spine loading and potential risk of injury as a function of gender under realistic lifting situations. Purpose: To evaluate the differences in spine loading between men and women when exposed to similar workplace demands. Study design: A laboratory study was conducted to investigate the biomechanical responses during realistic free-dynamic lifting tasks when subjects lifted from origins and destinations that were either fixed or set relative to the subject's anthropometry. Patient sample: Twenty men and 20 women asymptomatic for low back pain were recruited to participate in the study. Outcome measures: The three-dimensional spine loads were predicted from a well-established electromyography-assisted model. Methods: Both genders completed a series of symmetric and asymmetric (60-degree clockwise) lifts that originated from two shelf heights ("relative" to knee height and "set" at 35 cm from floor) and terminated at one of two destination heights ("relative" to waist and "set" 102 cm from the floor). Three levels of box weight were investigated (6.8, 13.6 and 22.7 kg). Results: Men had significantly greater compression forces than women (about 640 N). Loading differences between genders were further magnified by several of the workplace factors. The differences between men and women were even greater when lifting either of the heavier loads from the lower fixed shelf (more than 50% greater). Conclusions: It is apparent that men produce the greater loads on their spines during lifting. However, engineering controls, such as adjustable workplace layout or less weight lifted, may reduce or eliminate gender-specific differences in spine loads. Furthermore, the differences in spine loads appear to be a result of kinematic trade-offs and muscle coactivity differences in combination with unequal body masses between genders. However, when the loads were put into context of the expected tolerances of the spine, women were found to be at increased risk of injury, especially when lifting heavy loads or under asymmetric lifting conditions. Collectively, the results indicate the need to account for differences between the genders when designing the workplace.
Analysis of internal torso loading in asymmetric and dynamic lifting tasks
Occupational Ergonomics, 2017
BACKGROUND: Asymmetric and dynamic lifting is known to be one of the leading causes of occupational lower back disorders (LBDs). Biomechanical modeling has been utilized to investigate lifting task characteristics so that the task demands can be kept within a limit, and internal muscles and joints are not injured. OBJECTIVE: This study implemented AnyBody TM to analyze internal torso loading in asymmetric and dynamic lifting tasks. METHODS: A six-camera motion capture (mocap) system collected dynamic motion data of lifting 30 lb (13.6 kg) weight at 0º, 30º and 60º asymmetry. The mocap data drove the AnyBody TM model, and the study investigated the effect of the asymmetry. RESULTS: Erector spinae was the most activated muscle for both symmetric and asymmetric lifting. When lifting origin became more asymmetric toward right, erector spinae activity was reduced, but oblique muscles increased their share of activity to counter the external moment. Most muscle tensions peaked at the lift initiation phase except left external oblique and right internal oblique. Left external oblique played a minor role in the right asymmetric lifting task, and the difference of activation for right internal oblique may be due to variance of the motion. Surprisingly the lift asymmetry decreased both compression and shear forces at the L5/S1 joint. CONCLUSIONS: This finding contradicted the results obtained from other research studies. The reduction in spine forces is postulated to have resulted from the increased oblique muscles' share in the production of back extensor moment. Since these muscles have longer moment arms, they generated lesser spine force to counteract the external moment. The subject also tended to squat as lifting origin became asymmetric, which effectively reduced the load moment on the spine.
The effects of sex and handedness on lumbar kinetics during asymmetric lifting tasks: A pilot study
Proceedings of the 7th International Digital Human Modeling Symposium (DHM 2022) and Iowa Virtual Human Summit 2022 -
Manual material handling such as box lifting is a very common task that is used in the industrial and medical fields. It is widely accepted that manual lifting can potentially lead to low back injury. Asymmetric lifting, which involves twisting of the trunk, shifts trunk muscle activation and can increase the lower back loading on the spine thus further increasing the likelihood of injury. Other researchers have explored asymmetric lifting but have not considered the effects of handedness. Sex has also been considered as a factor related to low back injury, but majority of research work include only male subjects in literature. This work aims to examine the effects of sex, handedness, box load, and box origin on the maximum lumbar flexion/extension L5-S1 joint moments generated during two-handed box lifting so that safer lifting recommendations can be made for those tasks. Eight participants (sex: 4 women, 4 men; age:
Evaluation of spinal loading during lowering and lifting
Clinical Biomechanics, 1998
Objective. To estimate the three-dimensional spinal loads during various lifting and lowering tasks. Design. The in viva 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" of flexion to 00) and lowered (0" of flexion to 40") 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-l 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. Relevance This study revealed the importance of investigating lowering as well as lifting since these types of motions result in drastically different EMG-torque relationships and, ultimately, different spinal loading patterns. Furthermore, this study indicates the importance of taking into account differences in lifting style (trunk moments) and the coactivity of the trunk muscles when estimating loads on the spine.
Spine loading during asymmetric lifting using one versus two hands
Ergonomics, 1998
This study documented three-dimensional spinal loading associated with asymmetric lifting while using either one or two hands to perform the task. Lift asymmetry was de® ned as a function of the load origin relative to the sagittal plane of the body. Lifts occurred at 0, 30, or 608 oOEthe sagittal plane on both sides of the body (lifting from the right and from the left relative to the sagittal plane). Ten subjects lifted a 13.7 kg box from one of these origins to a sagittally symmetric destination. Spinal loads were estimated through the use of a validated EM G-assisted model. Spine compression and lateral shear forces increased as the lift origin becam e more asymmetric. However, spinal compression and lateral shear increased by about twice the rate when lifting from origins to the left of the sagittal plane com pared to lifting from origins to the right of the sagittal plane. Anterior-posterior spinal shear decreased as asymmetry increased with larger decreases occurring when lift origins occurred to the right of the sagittal plane. One-hand lifting changed the com pression and shear pro® les signi® cantly. Onehand lifts using the hand on the same side of the body as the load resulted in com pression forces that were approximately equal to those observed when lifting with two hands in a sagittally symmetric position. Anterior-posterior shear decreased and lateral shear increased under these conditions. These results re¯ect the trade-oOE s that must be considered among spinal forces during asymmetric lifting while using one or two hands. These ® ndings have signi® cant implications for task assessment interpretation and workplace design.
Does team lifting increase the variability in peak lumbar compression in ironworkers?
2012
Ironworkers frequently perform heavy lifting tasks in teams of two or four workers. Team lifting could potentially lead to a higher variation in peak lumbar compression forces than lifts performed by one worker, resulting in higher maximal peak lumbar compression forces. This study compared single-worker lifts (25-kg, iron bar) to two-worker lifts (50-kg, two iron bars) and to four-worker lifts (100-kg, iron lattice). Inverse dynamics was used to calculate peak lumbar compression forces. To assess the variability in peak lumbar loading, all three lifting tasks were performed six times. Results showed that the variability in peak lumbar loading was somewhat higher in the team lifts compared to the single-worker lifts. However, despite this increased variability, team lifts did not result in larger maximum peak lumbar compression forces. Therefore, it was concluded that, from a biomechanical point of view, team lifting does not result in an additional risk for low back complaints in ironworkers.
The Effect of Task Asymmetry and Number of Hands on Spinal Loading
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 1997
This study documented three-dimensional spine loading associated with asymmetric lifting while using either one or two hands to perform the task. Lift asymmetry was defined as a function of the load origin relative to the sagittal plane of the body. Lifts occurred at 0, 30, or 60 degrees off the sagittal plane on both sides of the body (lifting from the right and from the left relative to the sagittal plane). Ten subjects lifted a 13.7 kg box from one of these origins to a sagittally symmetric destination. Spinal loads were estimated through the use of a validated EMG-assisted model. Spine compression and lateral shear forces increased as the lift origin became more asymmetric. However, spine compression and lateral shear increased by about twice the rate when lifting from origins to the left of the sagittal plane compared to lifting from origins to the right of the sagittal plane. Anterior-posterior spinal shear decreased as asymmetry increased with larger decreases occurring when ...
Spine, 2001
Study Design. A repeated-measures in vivo experiment. Objective. To describe within-subject variability of spinal compression in repetitive lifting. Summary of Background Data. Epidemiology and failure mechanics suggest that peak loads may be more predictive of injury than average loads. Nevertheless, biomechanical studies usually focus on the latter. Methods. Ten healthy males performed 360 lifts in 1 hour of a 45-L crate, weighted with a stable 10-kg mass on 1 day and with an unstable mass (10 kg of water) on another day. The maximum compression force in each lift was estimated, using a simple inverse dynamics model and a single equivalent muscle model. Results. The individual distributions of maximum compression force were slightly skewed to the right (average skewness 0.67). Median and 95th percentile values were used to characterize the distribution. The median (50th percentile) compression ranged from 3375 to 6125 N, and from 3632 to 6298 N in the stable and unstable load conditions, respectively. The within-subjects peak (95th percentile) compression forces were from 405 to 1767 N and from 526 to 2216 N, respectively, higher than the median values. The peak values differed significantly between conditions, whereas the difference in medians did not reach significance. Only a limited trendwise (fatigue-related) variance could be demonstrated. Conclusion. Peak spinal compression by far exceeds median compression in repetitive lifting and can be affected by task conditions independently from the median. Therefore, the variability of spinal loads needs to be taken into consideration when analyzing and redesigning tasks that can cause spinal injuries.
2021
Lift‐to‐lift variability occurs in repetitive lifting tasks due to alterations in the lifting techniques used by the lifter, resulting in variability in lower back tissue loading. Understanding how trunk variability changes with time in the initial phases of a lifting bout may provide insights into the risk of injury during work startup. The purpose of this study was to quantify the variation of lifting kinematics and kinetics during the initial phase of a lifting bout. Twenty participants performed a repetitive lifting task continuously for 30 min. The load was equivalent to 10% of each participant's body weight and lifting was done at a rate of six lifts/ min. Kinematic variables (three‐dimensional range of motion, angular velocity, and angular acceleration) of the trunk were measured using the Lumbar Motion Monitor and a dynamic biomechanical model estimated peak L5/S1 moment and spine compression. The variances of these variables were compared across 10‐min intervals: 0–10 m...
Journal of Biomechanics, 2009
Low-back load during manual lifting is considered an important risk factor for the occurrence of lowback pain. Splitting a load, so it can be lifted beside the body (one load in each hand), instead of in front of the body, can be expected to reduce low-back load. Twelve healthy young men lifted 10 and 20-kg wide and narrow loads in front of the body (the single-load lifts). These single-load lifts were compared to a lifting condition in which two 10-kg loads (a total of 20 kg) were lifted beside the body (the splitload lift). Lifts were performed from an initial hand height of 29 cm with four different lifting techniques (stoop, squat, straddle and kneeling techniques). Using measured kinematics, ground reaction forces, and electromyography, low-back loading (3D net moments and spinal forces at the L5/S1 joint) was estimated. Lifting a 20-kg split-load instead of a 20-kg single-load resulted in most cases in a reduction (8-32%) of peak L5/S1 compression forces. The magnitude of the reduction was roughly comparable to halving the load mass and depended on lifting technique and load width. The effects of load-splitting could largely be explained by changes in horizontal distance between the load and L5/S1.