Lifting Height as the Dominant Risk Factor for Low-Back Pain and Loading During Manual Materials Handling: A Scoping Review

Identifying ergonomics practices currently used by grocery distribution centers

Grocery warehouse workers continue to experience high rates of musculoskeletal disorders largely due to the repetitive lifting performed during the product selection and palletizing process. This project aimed to describe ergonomics practices that have been implemented within grocery distribution centers in the United States that could help reduce musculoskeletal disorders. Ninety-seven management personnel from 30 distribution centers were interviewed regarding ergonomics practices in place within their respective facilities. Through this process 44 ergonomics practices were identified. Thirteen practices address how the facility is set up. Two practices focused on options within the warehouse's computer management system. Six practices targeted order selector tools. Seven practices focused on things that can be done in full-case pick operations. Eight organizational practices were identified that could facilitate ergonomics efforts. And finally, eight practices focused on reducing exposures to ergonomic hazards in piece-pick operations. For each identified practice implementation data were obtained.

The effect of height of lifting on dynamic postural control in low back pain patients and healthy subjects

Objectives

The study investigated the influence of starting load position during lifting on postural control in nonspecific chronic low back pain (LBP) and healthy volunteers.

Patients and methods

The cross-sectional study included 20 healthy males (mean age: 31.8±7.4 years; range, 18 to 55 years) and 52 male patients (mean age: 33.4±9.2 years; range, 18 to 55 years) with chronic LBP between February 2016 and April 2018. Postural control characteristics were assessed by a force plate system. Center of pressure signals were obtained at a frequency of 100 Hz, and the mean of three trials was calculated. The participants were told to place their feet hip-width apart on the force plate while standing barefoot. They were then asked to lift a box weighing 10% of their body weight from the ground to waist height and then from waist height to overhead with straight elbows. They moved the box at their selected speed. The examinations began upon the examiner's command.

Results

Results indicated a significant difference (p<0.001) in all postural control variables in chronic LBP patients who lifted a load at different heights. In addition, there was a significant difference between all of the postural control measures of this study in healthy participants during load lifting at different heights (p<0.05), with the exception of the mediolateral standard deviation of velocity (p=0.067).

Conclusion

Different lifting heights impact LBP patients' and healthy people's postural control differently. Postural control was more challenging during waist-to-overhead lifting in the patient group. This may be due to a stiffening strategy. The central nervous system reduces postural sway at higher centers of mass.

The highs and lows of lifting loads: SPM analysis of multi-segmental spine angles in healthy adults during manual handling with increased load

Introduction: Manual handling personnel and those performing manual handling tasks in non-traditional manual handling industries continue to suffer debilitating and costly workplace injuries. Smart assistive devices are one solution to reducing musculoskeletal back injuries. Devices that provide targeted assistance need to be able to predict when and where to provide augmentation via predictive algorithms trained on functional datasets. The aim of this study was to describe how an increase in load impacts spine kinematics during a ground-to-platform manual handling task. Methods: Twenty-nine participants performed ground-to-platform lifts for six standardised loading conditions (50%, 60%, 70%, 80%, 90%, and 100% of maximum lift capacity). Six thoracic and lumbar spine segments were measured using inertial measurement units that were processed using an attitude-heading-reference filter and normalised to the duration of the lift. The lift was divided into four phases weight-acceptance, standing, lift-to-height and place-on-platform. Statistical significance of sagittal angles from the six spine segments were identified through statistical parametric mapping one-way analysis of variance with repeated measures and post hoc paired t-tests. Results: Two regions of interest were identified during a period of peak flexion and a period of peak extension. There was a significant increase in spine range of motion and peak extension angle for all spine segments when the load conditions were increased (p < 0.001). There was a decrease in spine angles (more flexion) during the weight acceptance to standing phase at the upper thoracic to upper lumbar spine segments for some condition comparisons. A significant increase in spine angles (more extension) during the place-on-platform phase was seen in all spine segments when comparing heavy loads (>80% maximum lift capacity, inclusive) to light loads (<80% maximum lift capacity) (p < 0.001). Discussion: The 50%-70% maximum lift capacity conditions being significantly different from heavier load conditions is representative that the kinematics of a lift do change consistently when a participant's load is increased. The understanding of how changes in loading are reflected in spine angles could inform the design of targeted assistance devices that can predict where and when in a task assistance may be needed, possibly reducing instances of back injuries in manual handling personnel.

Virtual modelling and analysis of manual material handling activities among warehouse workers in the construction industry

BACKGROUND: Musculoskeletal risks (MSRs) are a major concern among construction warehouse workers due to the lifting, carrying and lowering of heavy loads. OBJECTIVE: The objective of this study was to reduce MSRs among warehouse workers in the construction industry using virtual modelling and analysis of activities. METHODS: A preliminary study was carried out using the Standard Nordic Questionnaire. Biomechanical analysis, Ovako Working posture Assessment System (OWAS) and Rapid Upper Limb Assessment (RULA) were used to analyse the material handling activities. Virtual modelling was used develop the manikins with autoclaved aerated concrete (AAC) blocks at different carriage modes and stacking heights for the analysis. RESULTS: The preliminary study results revealed a higher prevalence of risk at their lower back (73.24%) among the construction warehouse workers. Biomechanical analysis showed a higher risk at L4-L5 joint of lumbar spine during overhead and bending postures for stacking the blocks. Posture analysis results of OWAS indicated a lower risk in overhead carriage mode. Detailed analysis with RULA confirms this result. Mean compressive force values at stacking heights were showed a significant difference (p < 0.05) in 8, 13, 18 and 21 kg AAC blocks. However, stacking height with a range of 120–140 cm was found as safer to the workers by considering all block sizes. CONCLUSION: An ergonomic intervention based on safer stacking heights was developed to reduce MSRs to an acceptable range. It improves productivity of handling the AAC blocks by reducing the cycle time. The intervention can be adapted for handling of similar materials in the construction industry.

Exoskeleton Application to Military Manual Handling Tasks

OBJECTIVE

The aim of this review was to determine how exoskeletons could assist Australian Defence Force personnel with manual handling tasks.

BACKGROUND

Musculoskeletal injuries due to manual handling are physically damaging to personnel and financially costly to the Australian Defence Force. Exoskeletons may minimize injury risk by supporting, augmenting, and/or amplifying the user's physical abilities. Exoskeletons are therefore of interest in determining how they could support the unique needs of military manual handling personnel.

METHOD

Industrial and military exoskeleton studies from 1990 to 2019 were identified in the literature. This included 67 unique exoskeletons, for which Information about their current state of development was tabulated.

RESULTS

Exoskeleton support of manual handling tasks is largely through squat/deadlift (lower limb) systems (64%), with the proposed use case for these being load carrying (42%) and 78% of exoskeletons being active. Human-exoskeleton analysis was the most prevalent form of evaluation (68%) with reported reductions in back muscle activation of 15%-54%.

CONCLUSION

The high frequency of citations of exoskeletons targeting load carrying reflects the need for devices that can support manual handling workers. Exoskeleton evaluation procedures varied across studies making comparisons difficult. The unique considerations for military applications, such as heavy external loads and load asymmetry, suggest that a significant adaptation to current technology or customized military-specific devices would be required for the introduction of exoskeletons into a military setting.

APPLICATION

Exoskeletons in the literature and their potential to be adapted for application to military manual handling tasks are presented.

Tactile cues can change movement: An example using tape to redistribute flexion from the lumbar spine to the hips and knees during lifting

Given the appropriate cues, kinematic factors associated with low back injury risk and pain, such as spine flexion, can be avoided. Recent research has demonstrated the potential for tactile sensory information to change movement. In this study an athletic strapping tape was applied bilaterally along the lumbar extensor muscles to provide continuous tactile feedback information during a repeated lifting and lowering task. The presence of the tape resulted in a statistically significant reduction in lumbar spine flexion when compared to a baseline condition in which no tape was present. This reduction was further increased with the explicit instruction to pay attention to the sensations elicited by the tape. In both cases, the reduction in lumbar spine flexion was compensated for by increases in hip and knee flexion. When the tape was then removed and participants were instructed to continue lifting as if it was still present, the reduction in lumbar flexion and increases in hip and knee flexion were retained. Thus this study provides evidence that tactile cues can provide vital feedback information that can cue human lumbar spine movement to reduce kinematic factors associated with injury risk and pain.