Static Strength Prediction Program Research Articles

Redesign and ergonomic assessment of a chest-support baby walker.

Parents often use baby walkers (BWs) as assistive devices to improve their infants' independent movement and motor skill acquisition. However, the literature suggests that conventional baby walkers (CBW) may cause delays in an infant's ability to walk independently and musculoskeletal burden on parents. In the current study, a baby walker (RBW) with chest support was redesigned and ergonomically assessed during an infant-walking task. The anthropometric dimensions of 90 infants aged 7-11 months were measured in the city of Urmia, northwestern Iran. Following redesigning based on the results from expert panel meetings and prototyping of the RBW, 18 mothers (age: 28.33±4.27 and height: 163.75±5.32 and weight: 59.45±5.99) with their infants (9 boys and 9 girls) performed a simulated infant walking task in two experimental sessions using the CBW and RBW over a repeated measurements design. The infants' feet track patterns, including the number of steps and step distances were assessed via the image analysis of the footprints. The mothers' body posture and lower back spinal load were evaluated using Rapid Upper Limb Assessment (RULA) technique and 3D Static Strength Prediction Program (3DSSPP), respectively. Wilcoxon signed-rank tests showed infants walked more steps with the RBW (p = 0.002). Similarly, the distance between the infants' left heel strike (p = 0.008) and their right and left toe-off (p = 0.03 and 0.02 respectively) was also significantly lower in the RBW use. Additionally, the body posture of mothers was improved (RULA final score from 7 for CBW to 5 for RBW). Moreover, lower back compression and shear forces were reduced significantly (p = 0.002) by the RBW use. According to the feet track pattern, infants took more balanced steps when the RBW was used. In addition, mothers were subjected to less pressure on the lumbar region when they placed and lifted their infant from the RBW. However, further work is necessary to investigate potential long-term effects of the RBWs use.

Biomechanical evaluation of midwifery tasks and its relationship with the prevalence of musculoskeletal disorders

IntroductionAs an important occupational group in the healthcare system, midwives face various ergonomic risk factors such as musculoskeletal disorders (MSDs) risks. Moreover, an accurate job evaluation can help to design appropriate ergonomic interventions and more accurately estimate the probability of developing MSDs. Therefore, the present study aimed to investigate musculoskeletal discomforts and biomechanical stresses using the Three-Dimensional Static Strength Prediction Program (3DSSPP Ver. 7.1.3) to find the association of these factors with the prevalence of MSDs among midwives. Materials and methodsA total of 91 midwives with at least two years of work experience participated in this cross-sectional descriptive study. All midwifery duties were analyzed using the hierarchical task analysis (HTA) method. Moreover, time analysis was performed for this job, and data were collected using the Nordic Musculoskeletal Questionnaire (NMQ) and body mapping. The 3DSSPP software was used to investigate the forces acting on the lumbar region, and finally, the association of individual characteristics and the forces exerted on the body with MSDs was investigated. ResultsAccording to the results, the highest level of pain and discomfort was related to the back and neck regions. The software analysis of the four major midwifery tasks showed that the highest biomechanical forces were exerted on the L5/S1 disc during lifting the mothers from bed (to help them sit or walk) and breastfeeding training. Accordingly, only in the task of lifting the mothers and helping them to sit or walk, the balance status was inappropriate and critical due to the improper distribution of forces. The analysis of the associations between variables showed that biomechanical forces, age, height, body mass index, and job tenure were among the risk factors affecting MSDs. ConclusionAccording to the results of this study, MSDs were highly prevalent, especially in the neck and back regions; this can be attributed to the nature of midwifery tasks. The software analysis results of the tasks showed that the biomechanical forces on the spine in each of the tasks can be affected by the weight of the mother, the height of the bed, static posture, and the bending/twisting of the whole body. Compression and shear forces were among the risk factors that can affect MSDs. To prevent MSDs in midwives, it is appropriate to improve the workstations.

Compressive and Shear Forces of L5/S1 during Patient Transfer in Different Loads on Hands

Patient transfer is the primary cause of lower back pain among caregivers because it requires awkward postures and movements such as twisting, lifting, and lowering with heavy external loads such as body weight. To prevent lower back pain, the relationship between lumbar loads and external loads from patient weight should be investigated to explore the hazardous limits of external loads during patient transfer. However, this investigation requires frequent trials and heavier loads than the hazardous limit. Therefore, we have used a computational musculoskeletal simulation for patient handling without the actual measured load data of human subjects. A previous study used a musculoskeletal simulation of sit-to-stand assistance motion; however, this simulation did not consider twisting and lowering patient transfer. Hence, this study aims to investigate the relationship between lumbar loads and external loads during patient transfer, including twisting and lowering. The musculoskeletal simulation for this investigation was implemented using the 3D Static Strength Prediction Program. First, the implemented musculoskeletal simulation was validated by comparison with related research using actual measured motion data and an optical motion capture system. Furthermore, the relationship between lumbar loads (compressive and shear forces of L5/S1) and external loads during patient transfer was investigated using a validated musculoskeletal simulation. According to the results, the compressive and shear forces of L5/S1 during patient transfer exceeded the limits of safety when the external load was more than 40 kgf. These findings will contribute to the prevention of lower back pain due to patient transfer.

Ergonomics Evaluation in Designed Maintainability: Case Study Using 3 DSSPP

Abstract Maintainability is one of the design parameters (reliability, availability, maintainability, and safety (RAMS)) and maintenance is needed to keep the respective design in sustainable use. At the same time, the human is involved in the form of interface and interaction in an engineered product/system designed. Ergonomics is a multi-disciplinary science that considers human capabilities and limitations in a broader sense. The objective of this paper is to integrate ergonomics into the maintainability design process in order to facilitate maintenance operation in lesser; time, cost, easier operation as well as the well-being of human who is involved. In other words, good ergonomics lead to good economics and in a broader sense, sustainability. This investigation shows that designing comfortable workplaces and lesser workload for maintenance operators will be beneficial for the maintainability design process and also improve the meantime to repair MTTR. In order to evaluate the effect of designed work-place and workload on maintainers 3 D Static Strength Prediction Program (3D SSPP) that is commonly used as an ergonomics evaluation tool in scientific studies was applied.

Inertial Motion Capture-Based Whole-Body Inverse Dynamics.

Inertial Motion Capture (IMC) systems enable in situ studies of human motion free of the severe constraints imposed by Optical Motion Capture systems. Inverse dynamics can use those motions to estimate forces and moments developing within muscles and joints. We developed an inverse dynamic whole-body model that eliminates the usage of force plates (FPs) and uses motion patterns captured by an IMC system to predict the net forces and moments in 14 major joints. We validated the model by comparing its estimates of Ground Reaction Forces (GRFs) to the ground truth obtained from FPs and comparing predictions of the static model’s net joint moments to those predicted by 3D Static Strength Prediction Program (3DSSPP). The relative root-mean-square error (rRMSE) in the predicted GRF was 6% and the intraclass correlation of the peak values was 0.95, where both values were averaged over the subject population. The rRMSE of the differences between our model’s and 3DSSPP predictions of net L5/S1 and right and left shoulder joints moments were 9.5%, 3.3%, and 5.2%, respectively. We also compared the static and dynamic versions of the model and found that failing to account for body motions can underestimate net joint moments by 90% to 560% of the static estimates.

Postural Analysis on Manual Pine Resin Collecting Work: Lifting Index and L5/S1 Compression-Shear Forces

Even though pine oleoresin harvesting is labor-intensive forestry work involving manual material handling (especially lifting) and is massively carried out in Indonesia, there is a lack of ergonomics studies on manual pine oleoresin harvesting. This study focused on lifting-related postures in pine oleoresin harvesting. A Three Dimension Static Strength Prediction Program Version 7.1.0 was used to identify the injury risk on the lower back (lumbosacral joint, L5/S1) using biomechanical criteria (compression and shear forces) at extreme postures. Recommended Weight Limit (RWL) and Lifting Index (LI) were calculated for a comprehensive analysis. The exceeding compression and shear forces indicated that the L5/S1 injury risk on oleoresin collecting work (part of oleoresin harvesting) is high. The psychophysical analysis confirmed the findings, as several main postures in this work were categorized as intense manual lifting due to the excessive score of LI. A significant reduction in the L5/S1 compression and shear forces were shown at a simulation using a proposed load threshold (using the calculated RWL). Keywords: biomechanics, ergonomics, forestry work, manual lifting, oleoresin harvesting

A comparison between measured female linear arm strengths and estimates from the 3D Static Strength Prediction Program (3DSSPP)

This study performed a direct comparison between empirically measured female linear arm strengths and those estimated with the 3D Static Strength Prediction Program (3DSSPP). Linear arm strengths were collected from 15 female participants, at four hand locations and six primary directions (n = 360), and then estimated with 3DSSPP incorporating each participant's own segment lengths, body masses and joint strengths, and the measured arm postures from each trial to optimize the accuracy of 3DSSPP. In spite of this, the errors in 3DSSPP's estimated arm strength values were very high (RMS error = 56.0 N and 40.4%) and poorly correlated (r2 = 29.2%) with measured strengths. These results seriously question the accuracy of 3DSSPP to estimate female linear arm strengths and percent capable values, for the range of conditions tested, likely due to the overly simplified assumptions made to estimate triaxial shoulder strength.

Ergonomic Assessment of Low Back Loading Pattern During Occupational Lifting Task in a Lower Limb Amputee: Minimizing Injury Risk.

While the relationship between occupational task intensity and repetitive overuse injuries have been well studied and prescription/guidelines to assess and minimize risk of such injuries well established in the general healthy population, these aspects are not well understood in individuals with disabilities. In this practice-oriented paper, we use high a resolution sensor-data driven methodology to track muscle activation patterns and joint kinematics during a common lifting task in a unilateral lower limb amputee to gain a better understanding of the risk of injury during non-optimal lifting postures. The observed data from high resolution sensors are used to recommend optimized prosthetic device tuning. Further the participant specific low back compression loads calculated using Hand-Calculation Back Compressive Force estimation model (HCBCF) and the University of Michigan 3D Static Strength Prediction Program (3DSSPP™) model is used to identify the safe zones of joint loading during the lifting task.

중량물 취급 시 어깨 부하 평가에 대한 연구

Objective: The purpose of this study is to analyze the load on the shoulder in Manual Materials Handling (MMH).Background: According to the Korea Occupational Safety and Health Agency"s statistics on industrial injuries, Among the musculoskeletal patients in 2019, about 73.1% of patients were found to have physical pain due to the Manual Materials Handling (MMH) work process. In Korea, foreign evaluation criteria of materials handling have been employed without modification. Although a number of studies have been conducted on the degree of load on the lumbar spine (L5/S1) in materials handling, the research on the shoulder load is insufficient.Method: This study used the anthropometry data in the 1st, 50th and, 99th percentiles of Korean males aged 20 to 45. Also, 3D Static Strength Prediction Program (3DSSPP) software was used to analyze the load on the shoulder in materials handling.Results: The results of this study showed that as the horizontal distance between the worker and the center of the material increases, the load on the shoulder increases. Also, as the vertical distance increases, the load on the shoulder increases.Conclusion: The loads on the shoulder for 99th percentile male was relatively greater than those for 1st and 50th percentile male in the outstretched arm posture.Application: These results can be used as the basic data for the research of materials handling guidelines of the shoulder that considers physical characteristics for Koreans.

Development and validation of a cumulative exposure shoulder risk assessment tool based on fatigue failure theory

Objective To present a new risk assessment tool for shoulder intensive occupational tasks based on fatigue failure theory. Methods The tool estimates cumulative damage (CD) based on shoulder moments and loading cycles using an S–N curve derived from in vitro tendon fatigue failure tests. If multiple shoulder tasks are performed, the CD for each is summed. In the validation, 293 workers were evaluated for five separate shoulder outcomes. Logistic regression was used to assess the log CD against five shoulder outcomes adjusted for covariates including age, sex, body mass index (BMI), and plant site. Results Both crude and adjusted logistic regression results demonstrated strong dose-response associations between the log CD measure and all five shoulder outcomes (continuous ORs ranged from 2.12 to 5.20). Conclusions The CD measure of The Shoulder Tool demonstrated dose-response relationships with multiple health outcomes. This provides further support that MSDs may be the result of a fatigue failure process. Practitioner summary This study presents a new, easy-to-use risk assessment tool for occupational tasks involving stressful shoulder exertions. The tool is based on fatigue failure theory. The tool was tested against an existing epidemiology study and demonstrated strong relationships to multiple shoulder outcomes. Abbreviations MSD: musculoskeletal disorder; NORA: national occupational research agenda; RULA: rapid upper limb assessment; REBA: rapid entire body assessment; S-N: stress-number of cycles; EDL: extensor digitorum longus; DPC: damage per cycle; CD: cumulative damage; UTS: ultimate tensile strength; FTOV: first time office visit; 3DSSPP: 3-dimensional static strength prediction program; AS: visual analogue scale; BMI: body mass index; CI: confidence interval; Nm: newton-metre; LiFFT: lifting fatigue failure tool; DUET: distal upper extremity tool; OMNI-RES: OMNI resistance exercise scale.

Impact of the seated height to stature ratio on torso segment parameters

Ergonomic modelling programmes such as the Three Dimensional Static Strength Prediction Programme (3DSSPP) are valuable tools for assessing strength capabilities and risk assessment. These tools rely on accurate, representative inputs in the form of body segment parameters (BSPs). The upcoming version of 3DSSPP will employ BSPs for the torso, split into thoracic, lumbar and pelvis segments in order to more precisely determine spinal forces and injury risks. This study determines the impacts of age, body mass index and the estimated seated height to stature ratio (SHS) on these full and split torso parameters in a sample of working American adults. The results show that all of these metrics have significant relationships with the BSPs of interest, indicating that they must be accounted for when determining these parameters. A sensitivity analysis performed in 3DSSPP demonstrates that varying the parameters inputs will have large effects on L5/S1 compression force calculations. Practitioner Summary: Current anthropometric data sets for ergonomic applications do not account for wide ranges of age, BMI and overall body shape on segment parameter calculations. This study quantifies the associations of age, BMI and the seated height to stature ratio on full and split torso segment parameters. Abbreviations: 3DSSPP: Three-Dimensional Static Strength Prediction Program; BMI: body mass index; BSP: body segment parameter; BW: body weight; COM: centre of mass; DXA: dual energy x-ray absorptiometry; RG: radius of gyration; SHS: seated height to stature ratio; SL: segment length

Analysis of Musculoskeletal Disorders and Muscle Stresses on Construction Workers’ Awkward Postures Using Simulation

The negligence involved in musculoskeletal disorder (MSD) at construction sites results in high rates of muscle injuries. This paper presents findings identified by the MSD for each part of a worker’s body, categorizing the awkward postures of each body part, estimating muscle stresses, and establishing the benchmark using anthropometry and hand force data. MSDs and their corresponding frequencies were identified by administering the Nordic Musculoskeletal Questionnaire (NMQ) survey, which solicits responses regarding construction workers’ awkward postures. Musculoskeletal stresses were estimated using three-dimensional static strength prediction program (3D SSPP) biomechanical software. The new benchmarks were established for existing preventive measures using the anthropometry and hand force data. Workers suffering from different body muscle pains in awkward postures may be predicted using the compression forces magnitude, strength capability, and body balance. The model was verified by comparing its outputs with the survey analysis results. The study is of value to practitioners because it provided a means to understand the contemporary scenario of MSD and to establish a practical benchmark based on the physical capability of workers. It is relevant to researchers because it digitally predicts MSD and facilitates experimentation with different dimensions, thereby contributing to construction productivity improvement. Test cases validate the prediction method.

Process improvements using lean methodologies in a subassembly line

This research study focused on an engine subassembly line at a manufacturing facility. The objective of the study is two-fold: 1) to reduce takt time for engine build by implementing continuous improvement methodologies using lean principles; 2) to minimise the risks this subassembly line is currently prone to because of area congestion, safety issues and ergonomic concerns. Takt time was reduced by 25% by improving the layout using kaizen events based on the input obtained from time studies and motion studies (with spaghetti maps and heat maps). Failure mode effect analysis and three-dimensional static strength prediction program software were used to study the safety risks and ergonomic issues respectively and recommendations were implemented to improve the current working environment.

Evaluation of Quality of Life and Ergonomic Risks in Workers of the Furniture Sector in Southeastern Brazil

This study evaluated ergonomically the workers of a furniture industry making sofa structures, located in the city of Visconde do Rio Branco, Minas Gerais State, between August 2016 and December 2016, aiming to evaluate the quality of life and the ergonomic risks of the workers present. It was evaluated a population of 66 workers, including assemblers of sofa structures and carpentry machine operators, both males. Initially, all of these were submitted to the pain test, performed by means of questions regarding the greatest and least muscular discomfort, with the help of a map of the musculature of the human body. A sample of the workers with the highest rates of muscular pain was withdrawn from this population. The sample was submitted to WHOQOL-Bref (World Health Organization Quality of Life - Bref) questionnaire, which evaluates the perception of quality of life; After the kinesiological analysis of the work, observing the positions adopted and the assembly time of the structures of the sofa; the RULA method (Rapid Upper Limb Assessment), responsible for evaluate possible damage to limbs, such as the arm, forearm, wrist, neck, trunk and legs; and finally the biomechanical evaluation of static and postural forces, using 3DSSPP software (3D Static Strength Prediction Program). The results of WHOQOL-Bref questionnaire revealed that, in general, the perception of the sample about quality of life at work was classified as "very satisfactory" and the "physical environment was the one with the lowest degree of satisfaction. The kinesiological and biomechanical analyzes showed that the factors most critical to the work routine are related to wrist flexion, ulnar deviation and flexion of the indicator. However, based on static and postural forces, this activity can be developed without health risks by 97% of the workers. The load on workers during the working day did not prove to be crucial for triggering musculoskeletal disorders, so most workers are able to develop their work activities without health risks.

Forces Loaded on the Back of Manual Material Handling Tasks' Workers of Food Industries in Malard Using"3D Static Strength Prediction Program”

Introduction: Manual Material Handling tasks can cause fatigue in the short term and increase physical workload and musculoskeletal injuries in the long term. The present study was conducted to determine the amount of forces entered to the lower back in workers with manual material handling tasks.Methods: This descriptive-analytic study was conducted on 100 workers in food industries in Malard city in 2017. The Nordic questionnaire was used to determine the frequency of musculoskeletal disorders. The 3DSSPP was also applied to determine the amount of forces entered to the lower back of manual material handling tasks workers. Data analysis was conducted using SPSS (version 23)Results: we found that 24percent of workers had discomfort in at least one of their nine musculoskeletal muscles. The results of 3DSSPP showed that 30 and 34 percent of the compressive forces entered into L5/S1 and L4/L5 discs, respectively. In addition, the shearing force loaded on the L5/S1 disc was also found to be higher than the permissible limit eight percent of the participants. No significant relationship was found between the frequency of musculoskeletal disorders and the amount of compressive and shear forces entered to the lower back of workers.Conclusion: Based on NIOSH recommended limits, the amount of compressive and shear forces entered to the lower back in 3DSSPP showed that in 30 percent of manual lifting load tasks, the risk of injury to the lower back was moderate and this risk was low in 70 percent of tasks.

Postur Kerja dan Risiko Low Back Pain pada Pekerja Pasiran

One of the manual matrial handling jobs is the derivative work from the top of the truck. In working the workers use a tool that enggrong which is a short-handed shovel. Due to the use of employee enggrong work with stooped posture. This work posture raises the potential for low back pain in workers. This study is a cross sectional study with a sample of 9 participants. The purpose of research is to find potential risks of low back pain based on angle trunk when workers work sent down the sand by enggrong. Angle trunk which is predicted covering: 1 angle trunk flexion, 2) angle trunk bending, and 3) angle trunk twisting. Work posture data was taken using Microsoft KinectTM 3D camera and analyzed by using Siemen Jack 3D Static Strength Prediction Program (3DSSPP) software to predict angle trunk. The result of the analysis of the 6 work postures showed that worker's frequently employed posture had the average angle trunk flexion of 61.10 ± 10.090, angle trunk bending of 19.80 ± 6.740 and angle trunk twisting of 20.00 ± 9.030. The average angle trunk flexion at 87.28% of maximal angle is a major cause risk low back pain. So that it can be summed up the potential for low back pain on sand workers. Intervention ergonomics need to prevent and reduce potential risks happened low back pain on sand workers.

Enggrong Modification Reduces Low Back Pain Risk on Sand Workers

Material handling manual work is a job at risk to worker health and safety, errors in the manual procedure of manual material handling will result in health impacts in the short and long term. One of the manual jobs of material handling is the job of lowering the sand from the top of the truck. In working the workers use a tool in the form of enggrong which is a shovel with a short handle. Due to the use of employee enggrong work with a stooped posture. This work posture raises the potential for low back pain on workers. Low back pain is a pain and/or loss of workability as a long-term risk of postural errors in activity. Low back pain occurs on low back disc L4 / L5 or L5 / S1. This study used treatment by the same subject design with a sample of 9 participants. The purpose of the study was to find out the different forces in Low back disc L4 / L5 when the worker worked using standard enggrong (Period 1 / P1) compared to using modification enggorong (Period 2 / P2). The forces in the L4 / L5 Low back disc include 1) compression, 2) anterior/posterior shear, and 3) lateral shear. Work posture data was taken using Microsoft KinectTM 3D camera and analyzed by using Siemen Jack 3D Static Strength Prediction Program (3DSSPP) method to get the force on the low back disc. The results of the analysis of the 6 work postures P1 and P2, showed a significant decrease (p <0.05) in the average compression force in the low back disc L4 / L5 on the work posture using modified enggrong. Enggrong modification lowers compression in low back disc L4 / L5 by 38.73% (P1 2143.8 ± 411.3 N; P2 1320.2 ± 418.4 N), anterior / posterior shear 46.17% (P1 542, 6 ± 103.9 N, P2 292.1 ± 81.2 N), and lateral shear 29.69% (P1 31.2 ± 22.08 N; P2 16.6 ± 14.28 N) compared with the use of enggrong standard. The threshold value for compression 3400 N and anterior / posterior shear is 700 N, then the compression and anterior / posterior shear values in Period 2 are well below the threshold. Decrease in the press force in low back disc L4 / L5 is as a result of changes in work posture workers who work using modification enggrong. It can be concluded that the use of modification enggrong can decrease the compressive force in the low back disc L4 / L5 so as to reduce the low back pain occurs to the workers.

Ergonomic assessment of airport shuttle driver tasks using an ergonomic analysis toolset

This study aimed to (a) evaluate strength requirements and lower back stresses during lifting and baggage handling tasks with the 3D Static Strength Prediction Program (3DSSPP) and (b) provide additional analyses using rapid entire body assessment (REBA) and the NASA task load index (TLX) to assess the risks associated with the tasks. Four healthy female shuttle drivers of good health aged between 55 and 60 years were observed and interviewed in an effort to determine the tasks required of their occupations. The results indicated that lifting bags and placing them in a shuttle were high risk for injury and possible changes should be further investigated. The study concluded there was a potential for injury associated with baggage storing and retrieval tasks of a shuttle driver.

Ergonomic evaluation of standard and alternative pallet jack handless

AimTransportation of materials using a pallet jack pulled behind the operator is common due to the visual advantages while transporting fully loaded pallets. The objective of this laboratory study was to quantify muscle activity, posture, and low back compressive and shear forces while completing typical pallet jack activities using a standard handle that required one handed pulling of a pallet jack compared to an alternative handle that allowed for two handed pushing. MethodsParticipants (n = 14) performed six to ten trials of common pallet jack tasks (straight travel and turning) with each handle. Posture analysis of the trunk and right upper extremity was performed using Motion Analysis (Santa Rosa, CA, USA) and back compressive and shear forces were analyzed using 3D Static Strength Prediction Program (University of Michigan, Ann Arbor, MI). Activity of the upper trapezius (UT), pectoralis major (PM), flexor digitorum superficialis (FDS) and extensor digitorum (ED) muscles were recorded (Telemyo 2400 T, Noraxon, Scottsdale, Arizona) and normalized to percent reference voluntary contraction values. All outcomes were compared using the paired t-test. ResultsPeak and mean muscle activity of the PM (p < 0.001) and ED (p < 0.01) were significantly higher using the alternative push handle during all three tasks. There were larger compressive forces at L4/L5 (p < 0.08) and L5/S1 (p < 0.002) using the alternative handle, and greater shear forces using the standard handle at both L4/L5 (p < 0.0001) and L5/S1 (p < 0.000). DiscussionThe standard handle outperformed the alternative handle with regard to muscle activity. The alternative handle had significantly greater compressive forces at L5/S1 due to the pushing nature of the hand-handle interface, yet the standard handle increased shear forces at both L4/L5 and L5/S1 levels in the low back. ConclusionIn this analysis, there was not a clear benefit to using either handle in terms of trunk strength capacity and varied benefits and drawbacks to each handle when comparing compressive and shear forces in the low back. However, given favorable subjective reports described in a prior publication, and the increased reliance on dynamic versus passive force production, facilitating a workers' ability to push a pallet jack while travelling with large loads is worth further investigation.

Biomechanical Evaluation of a Bed Feature to Assist in Turning and Laterally Repositioning Patients

This study investigated the effects of hospital bed features on the biomechanical stresses experienced by nurses when turning and laterally repositioning patients. Turn Assist, a common feature in ICU beds that helps to rotate patients, and side rail orientation were evaluated. Manual patient handling is a risk factor for musculoskeletal injury, and turning patients is one of the most common patient handling activities. No known studies have evaluated bed attributes such as the Turn Assist feature and side rail orientation that may affect the stresses experienced by the nurse. Nine female nurses laterally repositioned and turned a 63-kg and 123-kg subject on an ICU bed while motion capture, ground reaction forces, and hand force data were recorded. Loading of the spine and shoulder was modeled using 3D Static Strength Prediction Program (3DSSPP). Spine compression and shear forces did not exceed recommended limits when turning or laterally repositioning. However, the mean pull forces required to manually laterally reposition even the 63-kg subject was 340 Newtons, more than 50% greater than limits established in psychophysical testing. Turn Assist considerably reduced spine loading and pull forces for both turning and laterally repositioning. Lowering side rails reduced spinal compression by 11% when turning patients. Laterally repositioning patients as part of turning may pose an injury risk to caregivers. Turn Assist reduces physical loading on nurses when turning and repositioning patients. Caregivers should consider using Turn Assist and other aids such as mechanical lifts or sliding sheets especially when turning patients requires lateral repositioning.