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Sex Differences in Glenohumeral Muscle Activation and Coactivation During a Box Lifting Task
Manual material handling is associated with shoulder musculoskeletal disorders, especially for women. Sex differences in glenohumeral muscle activity may contribute to women's higher injury risk by affecting shoulder load and stability. We assessed the effects of sex (25 women vs 26 men) and lifting load (6 kg vs 12 kg) on muscle activation during box lifting from hip to eye level. Surface and intramuscular electromyography were recorded from 10 glenohumeral muscles. Most muscles were more activated for the heavier box and for women. These effects were larger for “prime...
A comparison of lumbar spine and muscle loading between male and female workers during box transfers
There is a clear relationship between lumbar spine loading and back musculoskeletal disorders in manual materials handling. The incidence of back disorders is greater in women than men, and for similar work demands females are functioning closer to their physiological limit. It is crucial to study loading on the spine musculoskeletal system with actual handlers, including females, to better understand the risk of back disorders. Extrapolation from biomechanical studies conducted on unexperienced subjects (mainly males) might not be applicable to actual female workers. For male workers, expertise...
Two-dimensional biomechanical thumb model for pipetting
Manual pipetting imposes repetitive movements, high force, and awkward postures on the thumb, fingers, and wrist, increasing the risk of musculoskeletal injuries. The purpose of this study is to provide a linear regression model to estimate the optimal pipetting grip height based on the two-dimensional biomechanical static thumb model developed in this study. This biomechanical static thumb model uses hand anatomy and static equilibrium conditions to estimate internal tendon forces against a given external force. Based on the model, we conclude that the optimal grip height is 3 cm in males and...
The influence of external load configuration on trunk biomechanics and spinal loading during sudden loading
Sudden loading is a major risk factor for work-related lower back injuries among occupations involving manual material handling (MMH). The current study explored the effects of external weight configuration on trunk biomechanics and trunk rotational stiffness in the sagittal plane during sudden loading. Fifteen asymptomatic volunteers experienced sudden loadings using the same magnitude of weight (9 kg) with two different configurations (medially- or laterally-distributed) at three levels of height (low, middle and high). Results of this study showed that the medially distributed weight...
Occupational biomechanical risk factors for surgically treated ulnar nerve entrapment in a prospective study of male construction workers
Evidence was provided for forceful hand-grip work, with and without vibration, as a risk factor for ulnar nerve entrapment (UNE) surgery in a large cohort of Swedish construction workers. Several individual biomechanical factors comprising such work were associated with increased risk of UNE, including: increased grip force, upper extremity load, frequency of hand-held tool use, and hand arm vibration. Source: Jackson, J. A., Olsson, D., Punnett, L., Burdorf, A., Järvholm, B. et Wahlström, J. (2018). Scandinavian journal of work, environment & health . http://dx.doi.org/10.5271/sjweh...
Surface electromyography for risk assessment in work activities designed using the “revised NIOSH lifting equation”
The aims of this study were: to identify surface electromyography (sEMG)-based indices of trunk muscles acquired during the execution of lifting tasks designed using the revised NIOSH lifting equation and featuring a progressively increasing lifting index (LI); to study changes of these indices in relation to the LI; to evaluate the relationship between the identified indices and forces (FL5−S1) and moments (ML5−S1) at the L5-S1 joint. sEMG, kinematic and kinetic data of 20 male workers were recorded in three conditions. We computed the average rectified value (ARV), root mean square...
How does the biomechanical exposure of the upper body in manual box handling differ from exposure in other tasks in the real industrial context?
The assessment of biomechanical exposure during handling tasks in relation to other activities that are performed in industrial settings can be crucial to understand the biomechanical demands of manual box handling for the upper limbs. This study aims to evaluate the representativeness of the handling task to the upper body in comparison with the other tasks in a real setting, compare the biomechanical exposure between tasks, and identify the differences in exposure during manual box handling from job exposure. Twelve workers had biomechanical exposure assessed through trapezius muscle activity...
Effectiveness of a vacuum lifting system in reducing spinal load during airline baggage handling
Information on spinal loading for using lift assist systems for airport baggage handling is lacking. We conducted a laboratory study to evaluate a vacuum lift system for reducing lumbar spinal loads during baggage loading/unloading tasks. Ten subjects performed the tasks using the industry average baggage weight of 14.5?kg on a typical two-shelved baggage cart with or without using the lift system (i.e. lifting technique). Repeated measures analysis of variance (2 tasks × 2 shelf heights x 2 techniques) was used. Spinal loads were estimated by an electromyography-driven biomechanical model...
Effects of work surface and task difficulty on neck-shoulder posture and trapezius activity during a simulated mouse task
Objectives. The purpose of this study is to evaluate the influence of the work surface and task difficulty on the head, upper back and upper arm postures and activity of the descending trapezius during a simulated mouse task. Methods. Healthy female university students (N = 15) were evaluated. The work surface was positioned at elbow height (EH) and above elbow height (AEH) and the task difficulty was set at low (LD) and high (HD) levels. The postures were recorded by inclinometers. Trapezius activity was normalized by the maximum voluntary isometric contraction (MVIC). Results. Significantly...
A detailed description of the short-term musculoskeletal and cognitive effects of prolonged standing for office computer work
Due to concerns about excessive sedentary exposure for office workers, alternate work positions such as standing are being trialled. However, prolonged standing may have health and productivity impacts, which this study assessed. Twenty adult participants undertook two hours of laboratory-based standing computer work to investigate changes in discomfort and cognitive function, along with muscle fatigue, movement, lower limb swelling and mental state. Over time, discomfort increased in all body areas (total body IRR [95% confidence interval]: 1.47[1.36–1.59]). Sustained attention reaction...
Développement d’un système de mesures et d’un protocole de mesures permettant de quantifier l’exposition physique des manutentionnaires
L'objectif principal de ce projet était de combiner différents senseurs et instruments pour expérimenter, en laboratoire et sur le terrain, un système de mesures permettant d'estimer quantitativement l'exposition physique des manutentionnaires. Ce type de système pourrait éventuellement servir à évaluer objectivement l'efficacité d'approches de prévention. Un second objectif consistait à mettre au point une stratégie d'échantillonnage pour optimiser la mesure de l'exposition physique...
Inter-day reliability of surface electromyography recordings of the lumbar part of erector spinae longissimus and trapezius descendens during box lifting
Background: Low back pain and neck-shoulder pain are the most reported types of work-related musculoskeletal disorders, and performing heavy lifting at work and working with trunk rotation increase the risk of developing work-related musculoskeletal disorders. Surface electromyography (sEMG) provides information about the electrical activity of muscles. Thus it has the potential to retrieve indirect information about the physical exposure of specific muscles of workers during their actual work. This study aimed to investigate the inter-day reliability of absolute and normalized amplitude of sEMG...
NIOSH Lifting Equation App: NLE Calc
The National Institute for Occupational Safety and Health (NIOSH) Lifting Equation mobile application, NLE Calc, is a tool to calculate the overall risk index for single and multiple manual lifting tasks. This application provides risk estimates to help evaluate lifting tasks and reduce the incidence of low back injuries in workers. Source: https://www.cdc.gov/niosh/topics/ergonomics/nlecalc.html
Cumulative occupational mechanical exposures during working life and risk of sickness absence and disability pension
Prospective cohort study Using a biomechanical job exposure matrix combined with Danish registers, cumulative occupational mechanical exposures throughout life (ie, more years with heavy and frequent lifting, and kneeling work) predicted risk of long-term sickness absence among older workers. Importantly, heavy lifting throughout working life was associated with disability pension. Source: Sundstrup E, Hansen ÅM, Mortensen EL, Poulsen OM, Clausen T, Rugulies R, Møller A, Andersen LL. (2017). Scand J Work Environ Health . http://dx.doi.org/10.5271/sjweh.3663
Difference between male and female workers lifting the same relative load when palletizing boxes
A few biomechanical studies have contrasted the work techniques of female and male workers during manual material handling (MMH). A recent study showed that female workers differed from males mostly in the strategy they used to lift 15-kg boxes from the ground, especially regarding task duration, knee and back postures and interjoint coordination. However, the lifting technique difference observed in females compared to males was perhaps due to a strength differences. The objective of this study was to test whether female workers would repeat the same lifting technique with a load adjusted to their...
Evaluating the low back biomechanics of three different office workstations: Seated, standing, and perching
The objective of this study was to evaluate how different workstations may influence physical behavior in office work through motion and how that may affect spinal loads and discomfort. Twenty subjects performed a typing task in three different workstations (seated, standing, and perching) for one hour each. Measures of postural transitions, spinal loads, discomfort, and task performance were assessed in order to understand the effects of workstation interaction over time. Results indicated that standing had the most amount of motion (6–8 shifts/min), followed by perching (3–7 shifts...
Estimation of lumbar spinal loading and trunk muscle forces during asymmetric lifting tasks
Application of whole-body musculoskeletal modelling in OpenSim Large spinal compressive force combined with axial torsional shear force during asymmetric lifting tasks is highly associated with lower back injury (LBI). The aim of this study was to estimate lumbar spinal loading and muscle forces during symmetric lifting (SL) and asymmetric lifting (AL) tasks using a whole-body musculoskeletal modelling approach. Thirteen healthy males lifted loads of 7 and 12 kg under two lifting conditions (SL and AL). Kinematic data and ground reaction force data were collected and then processed by a whole-body...
Revised NIOSH Lifting Equation May generate spine loads exceeding recommended limits
The 1991 NIOSH Lifting Equation (NLE) is widely used to assess the risk of injury to spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses the predictive equations developed based on a detailed trunk musculoskeletal biomechanical model to verify whether the RWL generates L5-S1 loads within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in some studies). Fifty lifting activities are simulated here to evaluate the RWL by the NLE and the L5-S1 loads by the predictive equations. In lifting activities involving...
Cinématique et modélisation biomécanique de l’épaule lors de tâches de manutention
De récentes revues de la littérature épidémiologique montrent que travailler avec les bras en position levée augmente la probabilité de développer des troubles musculosquelettiques (TMS) aux épaules. Bien que l’origine et les mécanismes de TMS à l’épaule manquent d’évidence dans la littérature scientifique, réaliser une tâche avec les bras en position levée cause un chargement de la musculature de l’épaule plus important. Cependant, peu d’éléments...
Determining Safe Limits for Significant Task Parameters During Manual Lifting
This experimental study investigated the effect of lifting task parameters (i.e., lifting weight, frequency, coupling, asymmetric angle, and vertical, horizontal, and travel distances) for various dynamic human lifting activities on the ground reaction forces of workers. Ten male workers loaded containers from different levels asymmetrically during experimental trials. The experimental design evolved using Taguchi's Fractional Factorial Experiments. Three factors (lifting weight, frequency, and vertical distance) were observed to be significant. The results showed that vertical reaction forces...
The assessment of material handling strategies in dealing with sudden loading
The effects of load handling position on trunk biomechanics Back injury caused by sudden loading is a significant risk among workers that perform manual handling tasks. The present study investigated the effects of load handling position on trunk biomechanics (flexion angle, L5/S1 joint moment and compression force) during sudden loading. Eleven subjects were exposed to a 6.8 kg sudden loading while standing upright, facing forward and holding load at three different vertical heights in the sagittal plane or 45° left to the sagittal plane (created by arm rotation). Results showed that the increase...
Cost-efficient assessment of biomechanical exposure in occupational groups, exemplified by posture observation and inclinometry
Objectives : This study compared the cost efficiency of observation and inclinometer assessment of trunk and upper-arm inclination in a population of flight baggage handlers, as an illustration of a general procedure for addressing the trade-off between resource consumption and statistical performance in occupational epidemiology. Methods : Trunk and upper-arm inclination with respect to the line of gravity were assessed for three days on each of 27 airport baggage handlers using simultaneous inclinometer and video recordings. Labor and equipment costs associated with data collection and processing...
Les femmes manutentionnaires - Un point de vue biomécanique et ergonomique
Les manutentionnaires encourent des risques très élevés de blessures au dos. Afin de trouver des solutions à ce problème chronique, l’IRSST subventionne une programmation de recherche sur la manutention. Un premier projet issu de cette programmation a comparé les méthodes de travail des manutentionnaires experts et novices masculins et a dégagé des principes de manutention qui serviront de guide à l’élaboration d’un programme de formation. Le présent projet se penchera sur l’étude...
Demands on the Knee During Kneeling and Squatting Activities Common to Low-seam Mining
In 2009, the operating height of approximately one fourth of underground coal mines in the U.S. restricted mine workers to kneeling, crawling, and/or stooping posture to perform work [MSHA 2009). The large number of knee injuries to these workers is likely attributed to exposure to musculoskeletal disorder risk factors (prolonged kneeling, crawling, and twisting on one's knees). Therefore, the National Institute for Occupational Safety and Health has investigated three different biomechanical parameters (muscle activity of the knee flexors and extensors, pressure at the knee, and the net forces...
Physiological and Psychophysical Comparison Between a Lifting Task With Identical Weight but Different Coupling Factors
Adams, KJ, DeBeliso, M, Sevene-Adams, PG, Berning, JM, Miller, T, and Tollerud, DJ. Physiological and psychophysical comparison between a lifting task with identical weight but different coupling factors. J Strength Cond Res 24(2): 307-312, 2010-The objective of the revised NIOSH (National Institute for Occupational Safety and Health) lifting equation is to prevent or reduce lifting-related injuries. The coupling component of the equation relates to quality of the grip (i.e., hand-to-object interface) and can be rated good, fair, or poor. Good coupling is theorized to reduce lifting stress, whereas...
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