Low Back Loading Research Articles

Low Back Load Produced by Changing a Diaper at Various Bed Heights Experienced by Female Care Workers in a Nursing Home

Low Back Load Produced by Changing a Diaper at Various Bed Heights Experienced by Female Care Workers in a Nursing Home

The contribution of load magnitude and number of load cycles to cumulative low-back load estimations: A study based on in-vitro compression data

BackgroundCumulative low-back load is suggested to be associated with low back pain, possibly due to (micro-)fractures of spinal segments. Based on available in vitro data it can be assumed that, in order to predict spine segment failure from cumulative compressive loading, load magnitude should be weighted with an exponent higher than one, whereas the number of cycles should be weighted with an exponent lower than 1. The aim of the present study was to assess both exponents based on available in-vitro data. MethodsData on loading to fatigue fracture of spinal segments under cyclic compression in-vitro were used and converted to survival probability for 5 load levels and 5 levels of number of cycles. Three optimization procedures were used to estimate the exponent of load magnitude and load cycles separately, and load magnitude and load cycles combined. Goodness of fit was assessed by comparing the Akaike's Information Criterion (AIC) between models. FindingsThe best fit, based on AIC and average error per data point was obtained with weighting of load magnitude and number of load cycles with exponents of approximately 2.0 and 0.2, respectively. InterpretationThe results show that a combination of load magnitude and number of load cycles weighted with exponents of approximately 2 and 0.2 respectively provides a suitable measure of cumulative spinal compression loading. This finding may be of relevance for assessing cumulative low-back loads in studies on the etiology of low-back pain.

Validation of occupational estimates of cumulative low-back load

In most genuine industrial settings, it is not yet feasible to directly measure in vivo tissue loads, nor is it practical to estimate dynamic load-time histories using biomechanical models. Thus, data extrapolation techniques are often used for obtaining occupational estimates of shift or daily cumulative low-back load exposures. These techniques are reliant on the assumption that the observed duty cycle of apparently stereotypical work is consistent over long working durations. This investigation evaluated the validity of this assumption using a controlled laboratory-based repetitive lifting task. Nine men performed 30-minutes of sagittal plane repetitive lifting tasks. Upper body kinematics were captured during the tasks, and a two-dimensional dynamic biomechanical model was used to generate peak and cumulative estimates of low-back loads. Over the course of the 30-minute testing sessions, kinematic adaptations at the elbow were responsible for an 8% reduction in duty cycle duration while peak low-back load magnitudes remained consistent. Combining reductions in duty cycle duration with negligible changes in peak loading contributed to a small decrease (⩽ 10%) in cumulative low-back load over the final 20-minutes of lifting. However, when data extrapolation was incorporated to estimate a shift exposure it was found that these changes could overestimate occupational cumulative low-back loading exposures by 10–27% inferences made regarding the risk of low-back pain or injury reporting associated with exposure.

Cumulative Low Back Load at Work as a Risk Factor of Low Back Pain: A Prospective Cohort Study

Purpose Much research has been performed on physical exposures during work (e.g. lifting, trunk flexion or body vibrations) as risk factors for low back pain (LBP), however results are inconsistent. Information on the effect of doses (e.g. spinal force or low back moments) on LBP may be more reliable but is lacking yet. The aim of the present study was to investigate the prospective relationship of cumulative low back loads (CLBL) with LBP and to compare the association of this mechanical load measure to exposure measures used previously. Methods The current study was part of the Study on Musculoskeletal disorders, Absenteeism and Health (SMASH) study in which 1,745 workers completed questionnaires. Physical load at the workplace was assessed by video-observations and force measurements. These measures were used to calculate CLBL. Furthermore, a 3-year follow-up was conducted to assess the occurrence of LBP. Logistic regressions were performed to assess associations of CLBL and physical risk factors established earlier (i.e. lifting and working in a flexed posture) with LBP. Furthermore, CLBL and the risk factors combined were assessed as predictors in logistic regression analyses to assess the association with LBP. Results Results showed that CLBL is a significant risk factor for LBP (OR: 2.06 (1.32–3.20)). Furthermore, CLBL had a more consistent association with LBP than two of the three risk factors reported earlier. Conclusions From these results it can be concluded that CLBL is a risk factor for the occurrence of LBP, having a more consistent association with LBP compared to most risk factors reported earlier.

A comparison of productivity and physical demands during parcel delivery using a standard and a prototype electric courier truck

Courier drivers are at risk for the development of fatigue and Musculoskeletal Disorders (MSDs) due to frequent awkward lifting and carrying of parcels. A functional prototype of a redesigned courier truck represented a potentially valuable engineering control to reduce courier drivers' MSD risk. Specifically, the prototype courier truck was evaluated for its ability to reduce double-handling of packages between carts and the truck, decrease the lifting of carts on/off the truck and reduce lifting packages in awkward positions. Ten courier drivers performed a simulated delivery route with 18 stops while surface electromyography of the forearms, shoulders and lumbar spine were monitored with a simultaneous video recording. Low back loading for each lift was calculated based upon video analysis. The prototype courier truck showed substantial and statistically significant reductions in total delivery time (−29.5%), and the reduction was especially noticeable for stops using a cart. The cumulative compression and integrated electromyograms also showed reductions for the prototype courier truck. Peak and average loads did not, however, change appreciably. The prototype courier truck met the first three goals; however, it did not measurably affect the demands of lifting and moving packages within the truck itself. Further development is intended to address this issue. Relevance to industryThe redesign of this transportation equipment achieved some reductions in mechanical loading as well as improvements in productivity.

Estimating 3-D L5/S1 Moments During Manual Lifting Using a Video Coding System

The aim of the study was to investigate the validity and interrater reliability of using a proposed video coding system to estimate the dynamical 3-D L5/ S1 joint moment on the basis of four key frames from video clips of asymmetric lifting tasks. L5/S1 joint loading has been widely adopted to quantify low-back loading during lifting tasks. However, the measurement of L5/S1 joint loading usually requires a laboratory environment, which cannot be applied during field surveys. The validity of this system was investigated by comparing the estimated L5/S1 joint moments of various simulated lifting tasks with motion tracking system-based reference L5/S1 joint moments. The comparison showed that the video coding system yielded good estimates on peak moment (r = .91, average absolute error [AAE] = 20.3 Nm) and cumulative moment (r = .88,AAE = 22.5 Nm.sec) of the sagittal plane. The interrater reliability of this system was assessed among 10 raters who used this system. The intraclass correlation ranged between .51 and .89 for the moments of different planes. The results of the validity and interrater reliability analyses showed that the proposed video coding system could provide a good estimate of total L5/S1 joint loading on the basis of side-view video clips of the simulated lifting tasks. Although it was not as accurate as a motion tracking system for L5/S1 joint loading calculations, this approach can be an alternative for back load estimation for some lifting configurations when the use of motion tracking systems is not possible.

移動援助動作時の腰部負担評価を目的としたアセスメントツール (TAMAツール) の開発 : 上方移動版における妥当性と信頼性の検証

移動援助動作時の腰部負担評価を目的としたアセスメントツール (TAMAツール) の開発 : 上方移動版における妥当性と信頼性の検証

Kettlebell Swing, Snatch, and Bottoms-Up Carry: Back and Hip Muscle Activation, Motion, and Low Back Loads

The intent of this study was to quantify spine loading during different kettlebell swings and carries. No previously published studies of tissue loads during kettlebell exercises could be found. Given the popularity of kettlebells, this study was designed to provide an insight into the resulting joint loads. Seven male subjects participated in this investigation. In addition, a single case study of the kettlebell swing was performed on an accomplished kettlebell master. Electromyography, ground reaction forces (GRFs), and 3D kinematic data were recorded during exercises using a 16-kg kettlebell. These variables were input into an anatomically detailed biomechanical model that used normalized muscle activation; GRF; and spine, hip, and knee motion to calculate spine compression and shear loads. It was found that kettlebell swings create a hip-hinge squat pattern characterized by rapid muscle activation-relaxation cycles of substantial magnitudes (∼50% of a maximal voluntary contraction [MVC] for the low back extensors and 80% MVC for the gluteal muscles with a 16-kg kettlebell) resulting in about 3,200 N of low back compression. Abdominal muscular pulses together with the muscle bracing associated with carries create kettlebell-specific training opportunities. Some unique loading patterns discovered during the kettlebell swing included the posterior shear of the L4 vertebra on L5, which is opposite in polarity to a traditional lift. Thus, quantitative analysis provides an insight into why many individuals credit kettlebell swings with restoring and enhancing back health and function, although a few find that they irritate tissues.

移乗介助動作における腰部負担軽減方策

移乗介助動作における腰部負担軽減方策

A biomechanical investigation of forces applied to the lift truck steering wheel: effects of posture, gender and hand contact on cumulative low back loading

Hand contact forces on a typical lift truck steering wheel were quantified in a laboratory to determine their effects on low back loading. A single muscle equivalent link segment model (3D Match) was used to estimate cumulative loading exposure variables at the L4/L5 intervertebral disc with and without hand contact forces. Hand contact forces significantly decreased cumulative L4/L5 compression in forward bending (FB) for males by 32% and females by 14%. Cumulative L4/L5 compression in males (37,023 ± 2183 Ns) was not different from that in females (38,413 ± 2224 Ns). When excluding hand contact forces, males had significantly greater cumulative L4/L5 compression (55,165 ± 1593 Ns) in FB compared to females (43,255 ± 1753 Ns). Hand contact forces on mobile equipment controls might result in decreased cumulative L4/L5 compression, especially in awkward trunk postures. Females may be further predisposed to injury resulting from exposure to cumulative load.

The effects of caregiver experience on low back loads during floor and overhead lift maneuvering activities

This study investigated the effects of caregiver experience on peak external forces and moments generated at the L5/S1 joint of the low back when maneuvering loaded floor-based and overhead-mounted patient lifting devices. Twenty caregivers were divided into more-experienced and less-experienced groups based on the product of two factors: their years of lifting experience and the frequency of lifting the caregivers had done in the past. Ground reaction forces and moments as well as motion capture data were recorded while caregivers performed five different maneuvering tasks with both lifts in each of three conditions (caregiver subjects worked alone, as the primary caregiver in a pair, and as the secondary caregiver in a pair). Six outcome measures (net external forces and moments at the L5/S1 joint) were recorded. Multivariate analyses of variance of all net external forces and moments were done separately for the floor and overhead lifts. A significant effect of experience level was found for the floor lift ( p = 0.006) but not for the overhead lift ( p = 0.163). A follow-up univariate analysis of floor lift activities found significant differences between more-experienced and less-experienced caregivers for Turn, Push and Legs Up activities. Relevance to industry Previous work has shown that overhead lifts reduce the loads on caregivers compared to floor lifts. The findings of this study further underscore the need to purchase overhead lifts to protect less-experienced caregivers (including informal family caregivers) who are at increased risk of back injury when maneuvering floor lifts.

Estimation of low back moments from video analysis: A validation study

This study aimed to develop, compare and validate two versions of a video analysis method for assessment of low back moments during occupational lifting tasks since for epidemiological studies and ergonomic practice relatively cheap and easily applicable methods to assess low back loads are needed. Ten healthy subjects participated in a protocol comprising 12 lifting conditions. Low back moments were assessed using two variants of a video analysis method and a lab-based reference method. Repeated measures ANOVAs showed no overall differences in peak moments between the two versions of the video analysis method and the reference method. However, two conditions showed a minor overestimation of one of the video analysis method moments. Standard deviations were considerable suggesting that errors in the video analysis were random. Furthermore, there was a small underestimation of dynamic components and overestimation of the static components of the moments. Intraclass correlations coefficients for peak moments showed high correspondence (>0.85) of the video analyses with the reference method. It is concluded that, when a sufficient number of measurements can be taken, the video analysis method for assessment of low back loads during lifting tasks provides valid estimates of low back moments in ergonomic practice and epidemiological studies for lifts up to a moderate level of asymmetry.

An EMG-based model to estimate lumbar muscle forces and spinal loads during complex, high-effort tasks: Development and application to residential construction using prefabricated walls

Residential building construction is moving toward more industrialized construction methods (e.g., use of prefabricated wall or “panels”), yet remains one of highest risk sectors for work-related musculoskeletal disorders. The centralized design process inherent in the use of wall panels offers the potential for proactive control of musculoskeletal risks, consistent with the prevention-through-design (or PtD) philosophy. As part of an ongoing effort to incorporate ergonomics into panel design, estimates of low back loading and injury risk were needed over a range of tasks performed during panelized construction. Here, a free-dynamic, three-dimensional, electromyography-based model was developed to provide such estimates, which was a modification of an earlier, relatively coarser model. Specific modifications included a more detailed representation of lumbar muscle anatomy and contraction dynamics, high-pass filtering of electromyograms to better represent muscle activation levels, and an enhanced calibration procedure through which five model parameters are specified on an individual basis and used to estimate lumbar muscle forces. With these enhancements, the predictive ability of the model was assessed over a wide range of simulated panel erection tasks. Predicted model parameters corresponded well with values reported earlier. Reasonable levels of correspondence were found between measured and predicted lumbosacral moments, though predictive ability varied between tasks and rotation planes. Relevance to industry Wall panels are representative of the current trend toward increasing use of industrialized methods in residential construction. Model-based estimates can be used as part of a larger project to facilitate proactive design of residential construction using panelized walls in order to reduce musculoskeletal exposures and spine injury risks.

Investigation of low back pain in a non-hospital population of the coastline of the State of São Paulo

BACKGROUND AND OBJECTIVES: Low back pain is a prevalent complaint of multifactorial origins. To date, there have been no studies on the prevalence and characteristics of low back pain in the city of Santos, in the coastal region of the State of São Paulo, Brazil. The objective of the present study was to assess the profile of middle-aged individuals with low back pain from the general population aged 40-59 years, regarding gender, body mass index, regular physical activity and load handling. METHOD: The study design was prospective, exploratory and transversal, comprising 200 adults aged between 40 and 59 years, randomly selected as the study population. These individuals were sequentially approached by the researchers and asked whether they would agree to answer a medical questionnaire. No indication of the intention of researching low back pain was given before the individuals had agreed to participate. RESULTS: Out of 200 individuals (78 males and 122 females), 159 of them (60 males and 99 females) answered that they had experienced at least one significant and limiting episode of low back pain in their lives. A subgroup of 109 individuals (37 males and 72 females) had sought medical care for this painful episode. There were no statistically significant differences regarding gender, body mass index or number of hours sitting down at work and the presence of low back pain. There was a small positive correlation between low back pain and load handling at work, as well as a slight negative correlation between low back pain and regular physical activity. CONCLUSION: Low back pain was a highly prevalent condition in otherwise healthy individuals in our region.

The Relationship between the Nurses' Low Back Load and the Height of the Bed during Patient Transfer

The Relationship between the Nurses' Low Back Load and the Height of the Bed during Patient Transfer

Three-dimensional peak and cumulative L4/L5 spine loads and trunk postures during non-occupational tasks

Cumulative low back loading has been shown to be a risk factor for low back pain reporting in the workplace. Evaluation of tasks outside of work might offer insight into why workers continue to have low back pain and may report pain differentially even when doing the same job. This study utilized a video-based 3D posture sampling approach to document joint postures of 18 people over a 2-hour period while performing non-repetitive tasks in and around their own homes. A 3D rigid link segment model was used to calculate reaction forces and moments at L4/L5 and joint models were used to calculate joint forces. Average peak (4.0 kN) and cumulative (9.9 MN·s) compression force estimates indicate significant loads on the low back occur during non-occupational tasks, despite the fact that participants spent most of their time (86.2%) in neutral trunk postures. Cumulative anterior reaction shear force (440 kN·s) was found to be comparable to those documented for a wide variety of occupational tasks, when extrapolated to an 8-hour shift. To our knowledge, this study is the first to include a full complement of 3D low back forces and moments, in conjunction with an assessment of trunk posture, for non-occupational activities. The evidence suggests that considering 3D peak and cumulative low back loading during non-occupational tasks is warranted and may help to explain some of the variability in the reporting of workplace-related low back disorders despite extensive ergonomic intervention.

Continuous assessment of low back loads in long-term care nurses

Considerable effort has been spent evaluating aspects of low back injury risk in nursing yet comprehensive evaluation of all work tasks has been limited. The purpose of this study was to evaluate peak and cumulative lumbar spine loads experienced by personal support workers. A total of 20 female long-term care workers were observed and had trunk posture monitored via an inclinometer throughout their shift. When adjusted for an 8-h workday, workers experienced cumulative loads of 21.3 ± 4.6 MNs, 1.8 ± 0.6 MNs and 2.9 ± 1.4 MNs for compression, lateral and anterior shear, respectively. Patient care, unloaded standing, walking and miscellaneous tasks accounted for almost 80% of cumulative compression, while lifts and transfers accounted for less than 10%. Mechanical lift assists reduced peak loads and contributed minimally to cumulative loading. These findings suggest that both peak and cumulative spine loads should be considered when evaluating injury risk in the nursing profession. Statement of Relevance: This study has shown that tasks other than patient transfers and lifts are important in the assessment of low back injury risk in nurses. The method developed is a relatively straightforward approach that can be used to estimate peak and cumulative spine load to provide insight to risk of injury in many occupational settings.

Effects of training and experience on patient transfer biomechanics

Nursing is one of the professions at highest risk for the development of low back disorders, with patient handling identified as a leading contributor. The purpose of this study was to assess a component of the Back Injury Prevention Program (BIPP) that provided direct instruction on patient handling technique. Trunk kinematics and muscle activities were collected as indicators of low back loading. Novice participants (before and after instruction) and experienced nurses (previously trained) were monitored while they performed three selected patient transfers. Following BIPP instruction, muscle activity in novice participants was reduced by up to 18.1% MVE. Trained novices and nurses had generally smaller thoracolumbar spine angles by approximately 12° with lower variability in spine angle. Nurses had a smaller range of spine motion than novices combined with higher trapezius and deltoid activities, which may be a load reduction strategy for the back. The BIPP patient transfer instruction provided improved thoracolumbar biomechanics for new trainees and experienced nurses. Relevance to industry Mechanical lifts are not viable in all hospital or home care settings, thus manual patient handling training is still a necessary and important facet of initial and continuing nursing education. Back education and patient handling instruction provides a cost effective prevention strategy in nursing.

The influence of skill and low back pain on trunk postures and low back loads of shearers

Shearing is a rural occupation developing considerable spinal loads and carrying a high risk of low back pain (LBP). Although the workforce has a skill structure, interaction between skill, spinal loads and LBP is unknown. We examined whether skill and LBP influenced trunk postures and loads within a sample of 80 shearers representing shear skill levels. A progression from junior to open class demonstrated a 100% increase in productivity, less time in severe flexion, more time in neutral lateral bend, and more time in axially twisted postures, with no increase in cumulative compressive and anterior shear forces. LBP prevalence increased linearly from 10% for junior through to 76% for open class shearers. Shearers with a history of LBP generated greater cumulative right medio-lateral shear forces, greater left lateral bend and left axial twist moments. Skill-based training that reduces asymmetric forces may help reduce such high prevalence levels of LBP. Statement of Relevance: Shearing is an important and physically demanding rural occupation. It requires sustained flexed postures that generate considerable spinal loads and a high risk of LBP. This research examines how skill and a history of LBP it carries interact to influence trunk postures and spinal loads within a sample of shearers.

Trunk postures and peak and cumulative low back kinetics during upright posture sheep shearing

Sheep shearing is the most demanding occupation in the wool harvesting industry and is known to have a high prevalence of low back pain. While use of a commercially available trunk harness reduces load on the low back, the extreme trunk flexion associated with shearing still remains. A novel, upright posture shearing technique has been designed to allow a more neutral spine posture. This study assessed this upright technique and found significant reductions in both trunk flexion and cumulative low back loading when compared to either the traditional method or the use of the trunk harness. Moments about the shoulder tended to be higher while using the upright shearing technique and further investigation of shoulder kinetics will be required to assess whether this creates injury risk to the upper extremity. Despite increased shoulder moments, the reduction in flexion and cumulative loading with the use of the upright technique has the potential to reduce risk of low back pain among shearers.