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There is some evidence that performing farm chores may place youth at risk of musculoskeletal injuries. However, actual investigations of interventions for farm youth have been sparse. The objective of the current study was to investigate two different types of interventions (add-on handles) for shovels, potentially reducing the risk of injury in farm youth. A lumbar motion monitor was used to capture trunk posture and motion while the youth performed a simulated shoveling task—removal of material from an animal stall. Ratings of perceived exertion and comfort of use were also assessed. The results indicate add-on handles decreased sagittal flexion but increased twisting as compared to regular shovels. Perceived ratings were worse for shovels with add-on handles. Overall, there appears to be a trade-off between sagittal and nonsagittal motion and appears to have minimal impact on risk of low back injury. However, further research is necessary to determine the complete ramifications of this trade-off with respect to the biomechanical load within the low back and on other joints. [ABSTRACT FROM AUTHOR]

Previous research has provided evidence that farm youth performing farm chores may be at risk of developing a low back musculoskeletal injury. In order to reduce these risks, effective interventions for reducing the stressors that cause the injuries are needed. The objective of the current study was to investigate alternative wheelbarrow styles as an intervention for youth working to transfer material on the farm with respect to trunk motion and perceived exertion. A lumbar motion monitor was used to capture three-dimensional trunk kinematics while several wheelbarrow tasks (e.g., pushing, pushing over bump, and dumping) were performed by youth. Ratings of perceived exertion and comfort of use were also assessed. Results indicated a reduction in the sagittal trunk flexion and velocity was achieved by adding a push bar to the handles, in combination with three-wheels, or utilizing adjustable handles. However, these alterations had little impact in the predicted low back disorder risk levels. Additionally, the youths' perceptions of risk and exertion levels were greater for these alternative wheelbarrows than for the regular wheelbarrow. Therefore, the mismatch between perception and kinematic response will probably affect usage of the alternative wheelbarrows. While the results indicate that alternative wheelbarrow designs can reduce the awkward postures and motions during wheelbarrow tasks, further research into the effectiveness of these interventions, including spine loading and long long-term use, is necessary. [ABSTRACT FROM AUTHOR]

Ergonomic job analysis commonly applies static postural and biomechanical analysis tools to particular postures observed during manual material handling (MMH) tasks, usually focusing on the most extreme postures or those involving the highest loads. When these analyses are conducted prospectively using digital human models, accurate prediction of the foot placements is critical to realistic postural analyses. In automotive assembly jobs, workers frequently take several steps between task elements, for example, picking up a part at one location and moving to another location to place it on the vehicle. A detailed understanding of the influence of task type and task sequence on the stepping pattern is necessary to accurately predict the foot placements associated with MMH tasks. The current study examined the patterns of foot motions observed during automotive assembly tasks. Video data for 529 pickup and delivery tasks from 32 automotive assembly jobs were analysed. A minimum of five cycles was analysed for each task. The approach angle, departure angle, hand(s) used, manipulation height and patterns of footsteps were coded from the video. Object mass was identified from the job information sheet provided by the assembly plant. Three independent raters coded each video and demonstrated an intraclass correlation coefficient of 0.54 for identification of the configuration of the lower extremities during terminal stance. Based on an analysis of the distribution of stepping behaviours during object transitions (pickups or deliveries), a transition classification system (TRACS) was developed. TRACS uses a compact notation to quantify the sequence of steps associated with a MMH transition. Five TRACS behaviour groups accounted for over 90% of the transition stepping behaviours observed in the assembly plant. Approximately two-thirds (68.4%) of the object transfers observed were performed with only one foot in contact with the ground during the terminal posture. The results from this paper suggest that a predictive model for choosing a transition stepping behaviour, coupled with a model to scale the selected foot behaviours, is needed to facilitate accurate prospective ergonomic analyses. This study proposes a method for categorising the stepping patterns associated with MMH tasks. The influence of task type and task sequence on the stepping patterns observed during several automotive assembly tasks is discussed. For prospective postural analyses conducted using digital human models, accurate prediction of the foot placements is critical to realistic postural analyses. [ABSTRACT FROM AUTHOR]

This study investigated sources of variance in exposure to risk factors for knee pain in a variety of highway construction trades, operations, and tasks. Over 15,000 discrete observations of leg postures and weights handled were made on 120 construction workers in five construction trades, in nine operations over 79 days. The contributions of trade, operation, task, and worker to the variability in work time spent kneeling, squatting, and carrying loads were evaluated with multilevel random effects models. Construction operation and task explained about 20% to 30% of total variation in kneeling, squatting, and carrying loads. There was a large unexplained component of variance thought to represent day-to-day variability of exposure within task. Reliable assessments of knee exposures require multiple days to accommodate the high variability of exposures among operations and tasks and over time. These sources of variability should be carefully considered in efforts to estimate exposures to knee loading for epidemiologic or intervention studies. Homogenous exposure groups are not easily defined from the readily available organizational features of construction work. [ABSTRACT FROM AUTHOR]

It has not yet been established whether an age-related organization of the work and rest times for order-pickers working in deep cold-storage depots with chill room and cold store is necessary or not. In order to assess the physical effects of order-picking of cold food at about +3°C and of frozen food at about -24°C, 30 male subjects (Ss) were classified into two age groups (20- to 35-year-olds and 40- to 65-year-olds). Their body core temperature was taken every 15~min at the tympanum, and the skin temperature was measured at several positions during whole-day working shifts. The discontinuously registered temperature at the tympanum yielded a decrease of up to 1.5K in the case of the younger Ss and of up to 2.2K for the older Ss in comparison to the value at the outset. A complete warming-up during the breaks was often not possible. The slight falling of the core temperature during the work in the cold store, measured for both age groups to a different extent, could be compensated by all Ss during the breaks. There were no age-related differences in the results of the measured skin temperatures. Significantly lower temperatures were recorded merely at the nose as well as at the fingers and the toes when working in the cold store. The work in the chill room can be considered as unproblematic. [ABSTRACT FROM AUTHOR]

This study examined the association between circumstances of occupational same-level falls and the risk of wrist, ankle and hip fracture in women over 45 years of age. Cases of fractures and matched controls who suffered non-fracture injuries, all from same-level falls, were selected from workers' compensation claims data. Cases and controls were matched on age, season of fall, industry and state. Information was obtained about manual material handling, fall hazard, initiating event and fall location. Falls during pushing/pulling were associated with increased wrist fracture risk. Falls due to tripping were associated with increased wrist fracture risk, but decreased risk of ankle fracture. Falling outdoors was associated with increased wrist and ankle fracture risk. Increasing age was associated with increased injury risk from tripping-initiated vs. slipping-initiated falls. Few circumstances increased risk of fracture at multiple sites, indicating that they affect risk of fracture by primarily affecting point of impact. The proportion of female workers over 45 years of age, who are at increased risk of fracture, is increasing in developed countries. This study examined the associations between circumstances of falls and wrist, ankle and hip fracture risks among these workers and found that the associations differed by fracture sites. [ABSTRACT FROM AUTHOR]

In spite of the advanced technology, manual material handling tasks are done frequently and the incidence rate of low back disorders is still high. Classification of industrial jobs related to low back disorder risks has therefore great potential to prevent injuries. In this study, industrial jobs have been classified into two categories as “low risk” and “high risk” using neuro-fuzzy classification. Neuro-fuzzy classification has obtained better results than previous studies which used the same experimental data. Furthermore, “IF-THEN” type fuzzy rules have been extracted easily from the results to analyze potential risk factors. Ergonomic interventions can be done by means of the obtained rules for future reduction in back injuries. [Copyright &y& Elsevier]

The article presents a study on the biomechanical reaction of a lumbar intervertebral disc to manual lifting conditions. It revealed that lifting the box from a maximal lateral flexed posture up to waist level developed the biggest translational and rotational movements. The study concluded that asymmetric lifting engaging lateral bending of the trunk made large motions that might induce localized disc tissue injury.

This paper explores the use of subjective perception tasks and its correlations with biomechanical data in the evaluation of manual material handling. Three main dimensions were considered for perception: physical regroups sensations issued from a specific body area; operative regroups feelings related to the execution of the task; and performance regroups feelings that involve a judgement on the execution or reflect overall sensations. The following questions were then explored. To what extent are perception data related to biomechanics data? Do both approaches lead to similar conclusions or interpretations when effect of practice, format and off-centre were tested? How can they complement one another? The task consisted of transferring 50 series of three 15 kg loads in order to verify the impact of free practice, format (box/cylinder) and load centre of gravity position. Eleven subjects rated perception on a CR-10 scale (Borg 1982) after each series. The session was completed with an interview on perception. The net resulting moment was systematically found to be the best correlated with data perception. While all physical and performance items corresponded in various ways to biomechanics data, perceptions associated with operative dimension appeared to be less related with biomechanical data. As regards the impact of practice, format and off-centre, both approaches would lead to the same conclusions, except for the effect of the off-centre. Verbal data add rational information about how or why perception can or cannot be reflected in biomechanics data. How both approaches can be matched more closely in manual handling is discussed. [ABSTRACT FROM AUTHOR]

Abstract: A study on combined manual materials-handling tasks performed on floors under three friction levels was conducted. Eight male subjects participated in the study. The maximum acceptable weight of handling, including lifting, carrying for 3m, lowering, and walking 3m back at twice per minute was determined. The subject then performed the same tasks for 10min. Heart rate, Vo2, energy efficiency, perceived sense of slip, and rating of perceived exertion for whole body strain were measured. The results showed that the effects of friction level on the maximum acceptable weights of handling, perceived sense of slip, Vo2, and energy efficiency were statistically significant (p⩽0.0006). As the friction level increased from low to high, the maximum acceptable weights of handling increased from 8.15 to 9.34kg. The energy efficiency on the low friction condition (12.58kg/L/min) was significantly lower than those of the medium (15.73kg/L/min) and high (15.38kg/L/min) friction conditions. The perceived sense of slip was the highest (5.44) on the low-friction condition, followed by the medium-friction condition (3.58), and last the high-friction condition (1.84). The implication of this study was that friction level should be regarded as one of the major environmental factors in designing MMH tasks as it affected both physiological and psychophysical responses of the subjects. Low-friction footwear–floor interface should be avoided as it resulted in not only high scores of perceived sense of slip but also in low-energy efficiency utilized in the body. [Copyright &y& Elsevier]

This study examined an existing industrial workstation at an automobile assembly plant using computer aided ergonomics and digital human models. The purpose of this evaluation was the development of a motion capture-based methodology for evaluating workstations to identify potential design issues that could result in musculoskeletal injury in a real work environment. An ergonomic risk assessment was conducted on a sample of operators performing a lifting task manually and using an assist device. An optical motion capture system was setup and calibrated in the industrial workplace to collect motion data. UGS™ JACK digital human modelling software was used for the computer-based ergonomic analysis to evaluate the potential injury risk of the current task, considering difference between using and not using the assist device. The work tasks were decomposed into subtasks before analysis. Muscle activity was also measured by wireless electromyography (EMG) in order to identify physiological indicators of stress and strain. The results suggest although using the assist device decreased injury risk potentially, use of the assist device had an adverse impact on the productivity of the assembly line. Based on the findings of this study, the methodology appears to be appropriate for assessing and predicting potential risks associated with the design of industrial workstations and work tasks. The results also highlight tradeoffs in using an assist device which can decrease injury risk in some cases, while having an adverse impact on the productivity of the assembly line. [ABSTRACT FROM AUTHOR]

Abstract: In developing a motion prediction model it is important to initially consider the sources of variability that a model should reproduce. This initial step is followed by model evaluation, where the variability predicted by the model can be a useful test parameter. An existing lifting-motion dataset collected under controlled laboratory conditions was employed here to evaluate quantitatively some important sources of variability for lift motion modeling. The main source of variability was the segment being analyzed, which accounted for more than 20% of the overall variability. There was substantial left–right symmetry in individual segment variability estimates, which were largest for the upper arm segment and tended to be larger for the upper limbs than the lower limbs. Task-related factors accounted for variability mainly as a function of the segment being considered. Within-participant variability contributions to the dataset were relatively small, whereas the contribution of between-participants variability was dependent on the segment (as large as 50%) and could indicate different lifting strategies across participants. Variability was found to remain relatively constant across the different stages of the lifting movements. Implications of these results for the development and evaluation of motion prediction models are presented. Specifically, while task characteristics may be important modifiers of the mean segment trajectory during a lifting movement, their influence on variability differs based on the segment that is being considered. The relevance of the findings is discussed in terms of their utility in the ergonomic design of tasks and work spaces. [Copyright &y& Elsevier]

The article assesses some of the individual and occupational risk factors contributing to introduction or intensification of low back pain among employees. The highest frequency of low back pain was observed in the age of 30-34 years old. Carrying different loads requires various postures in respect of the body posture.

Objective : To critically appraise the observational studies linking cumulative spinal loading and lower back disorders (LBD) among workers engaged in manual material handling and to explore the association between cumulative spinal loading and LBD through a meta-analysis of papers reported in the published literature. Background : Although studies have indicated a definitive relationship between long-term exposure to manual materials handling and LBD, little is generally known about the validity of the cumulative exposure assessment methods used for predicting the risk of LBD. Methods : A comprehensive electronic search on the subject was conducted. The articles found from the search were critically appraised from an epidemiological standpoint. The strengths and weaknesses of the studies were documented. A quantitative assessment was performed for the meta-analysis estimate using the fixed-effect and random-effects (Dersimonian and Laird method) models. The assessments were conducted in two ways: with a standard approach that does not consider study quality and with a modified method that allows weighting scores to be calculated based on the rating of the quality of each study. Results : The electronic search resulted in identification of four epidemiological papers, three of which provided sufficient information for an assessment of epidemiological quality and two of which provided sufficient data to conduct a meta-analysis. The results showed that the methodological quality of the studies ranged from poor to marginal. Without considering the overall study quality for the exposure data, (1) there were substantial differences between the three studies that were rated for epidemiological quality as evidenced by the significant heterogeneity testing at the 10% level and (2) the difference in the mean exposure values between the study and control groups (i.e. summary mean difference) was significant at the 5% level for both the fixed-effect and random-effects models. After accounting for overall study quality, the heterogeneity was reduced but still significant at the 10% level and the summary mean difference was greater than that without the quality score. The meta-odds ratio for LBD outcomes was 1.66 (95% confidence interval using quality scores  =  1.46–1.89). Conclusions : The preliminary findings suggest that there likely is an association between cumulative spinal loading and LBD. Further, there are considerable differences among the studies in terms of exposure assessment techniques. A subsequent paper (Part II of this research) provides an in-depth analysis of cumulative spinal loading exposure methods and discusses critical issues related to their reliability and validity for estimating force distribution and practicality for field measurement. [ABSTRACT FROM AUTHOR]

Objective : The goal of this paper is to review and discuss methodological issues related to cumulative spinal loading exposure assessment methods. Background : Research has indicated that there likely is an association between integrated spinal loading and lower back pain. A number of studies have been conducted to evaluate cumulative load; however, comparisons between studies is difficult due to the use of different methods for the assessment of cumulative spinal loading. Methods : A comprehensive electronic search was conducted to locate articles dealing with methods of cumulative spinal loading estimation. The articles were evaluated with respect to methods for obtaining postural data, methods for estimating spinal loads, methods for integrating loads over time and spinal load parameters to be measured. Results : Thirteen articles were located. A summary of the methods used to estimate cumulative spinal load is described and evaluated. Conclusions : There is a pressing need for integrated spinal loading methods that are reliable, valid and practical for use in large occupational epidemiological studies. A number of research needs were outlined aimed at improving the ability to use cumulative load to predict risk of low back disorders due to manual material handling. [ABSTRACT FROM AUTHOR]

While heavy lifting has been identified as an important risk factor for low back disorders, little is known about workplace spatial layout – the relative positions of shelves and the impact of this on spine loads. The objective of the current study was to investigate how the relative positions of the load origin and destination impact three-dimensional spine loads. Seven females and seven males lifted an 11.4  kg box from an origin shelf to a destination shelf, each defined by height (elbow, knee and shoulder level) and asymmetry (60° clockwise, sagittally symmetric, 60° counter-clockwise) while their spine loading was assessed by an electromyographic-assisted model. The results indicated that the starting and destination heights and starting task asymmetry all had significant impact on spine compression (with an increase of between 400 and 1900  N when compared to the most neutral position) and lateral shear (with a 100 to 150  N increase) while the destination height impacted the anterior – posterior shear forces (with up to 400  N increase). The results of the current study emphasize the importance of proper workplace spatial layout, specifically the importance of specifying starting position of the load relative to the destination. Adjustment of the starting position will impact the three-dimensional spine loads while the destination height and asymmetry influence the shear forces. Furthermore, the influence of the specific pathway (origin relative to destination) indicates there may be a potential preparatory muscle response leading to the loads on the spine. Thus, the pathway of the box plays an important role in the spine responses during lifting, in that longer and non-neutral pathways increase spine loads – indicating the importance of the relative position of the origin and destination shelf. [ABSTRACT FROM AUTHOR]

Discusses a study on the risk of musculoskeletal disorders among youths who perform physically demanding farm activities. Use of the lumbar motion monitor to record trunk movements while performing routine manual material handling tasks; Association of high injury risk jobs in industrial workplaces; Quantification of physical demands of tasks performed on farms.

The objective of this study was to assess the affect of pallet location on torso kinematics during lifting. Participants transferred 11.3 kg boxes to pallets at two orientations and two distances from a constant lift origin. When reorienting the pallet from 180° to 90°, torso twist, lateral and sagittal torso kinematics increased when palletizing to various locations on the pallet when keeping the pallet distance far. Torso flexion increased slightly at the lowest level on the pallet independent of the pallet distance. When keeping the pallet distance close, torso twist kinematics decreased only when palletizing to the highest and closest position of the pallet. When reorienting the pallet from 180° to 90° adjacent to the lift origin, the best strategy to reduce torso kinematics appears to be to eliminate the transferring of loads to the lowest level of the pallet, and keeping the pallet close to the lift origin. [ABSTRACT FROM AUTHOR]

Many clinicians and employers utilise work-related assessment tools for the purposes of identifying whether or not the performance of a specific job exposes an individual to a heightened risk of developing a low back injury. However, research has shown that some of these tools have not been assessed for validity or reliability, and thus may not accurately assess the risk associated with a particular activity. An example of a test employed by some Australian private industries is the Work Capacity Assessment Test, which is a procedure that is commonly used to screen potential employees and evaluate those workers returning to the workplace following injury. This research was designed to simulate the lifting component of the Work Capacity Assessment Test and involved a series of lifts ranging from 2.5 kg to 22.5 kg. Six subjects performed this task, whilst being assessed using two-dimensional videography and surface electromyography. The two-dimensional kinematic data were input into the 4D WATBAK software to quantify the compression forces acting between L4 and L5 during each performance. Results of this study showed that spinal compression and paraspinal muscle activity increased incrementally from the 2.5 kg lift to the 22.5 kg lift, whilst abdominal muscle activity also increased across the lifts. This study demonstrated that lifting masses of 22.5 kg or more can produce loads on the spine that are considered potentially hazardous, when compared to safe lifting guidelines, and indicated that there is a clear concern for the use of such lifting tasks in the evaluation of workers following injury. [ABSTRACT FROM AUTHOR]

The aim of the present study was to develop statistical models of perceived effort at the shoulder and torso levels associated with manual load transfer tasks. The motions were directed from a home location toward one of twenty-two target shelves distributed in the right hemisphere. A total of 2149 ratings were obtained from 31 subjects for effort perception at the selected joints, using a ten-point modified Borg scale. Regression models, developed for the perception associated with each body part, included target locations (azimuth, height and distance), posture constraints (standing or sitting), task types (one or two handed transfer conditions), and demographic and anthropometric measures (stature, body weight, gender, and age) as parameters. The models provide a prediction of effort perception with adjusted r -square coefficients of 0.41 and 0.50 for the shoulder and torso, respectively. The results indicate that space and posture interact in a complex way to affect the rating of perceived effort, and are in agreement with the hypothesis that the 'sense of effort' is primarily associated with the efference copy of the descending motor command. Since a level of effort is not associated with a unique pattern of motor command, it is proposed that effort perception is likely to result from a summation of the components of the motor command. The models can be applied to optimize the spatial organization of the work environment in an attempt to reduce the risk of musculoskeletal injury. [ABSTRACT FROM AUTHOR]

The incidence of low back pain has continued to increase in modern society, despite the considerable amount of scientific research that has aimed to isolate its exact aetiology. Although low back pain is still largely idiopathic, research has identified over one hundred risk factors for the condition. Of these risk factors, manual material handling tasks are perhaps the most widely explored within the biomechanical literature, as these tasks have been associated with high mechanical stresses on the lower back. Numerous technique-related variables have been addressed by researchers, whilst the influence of intra-abdominal pressure has also been considered. In addition to this, the implications of variations in the size and structural composition of the load have also been assessed. However, low back pain continues to pose a significant threat to the financial stability and happiness of millions of people worldwide. In addition, a number of functional work capacity assessment tests use lifting as a method for assessment of return to work condition. Many of these tests are not standardised and do not consider the implications of low back loading. Therefore new research attempts in this area are justified and should aim to identify the extent of the association that exists between the known risk factors and the incidence of low back pain. [ABSTRACT FROM AUTHOR]

Although there have been numerous studies evaluating the difference between stooped and squat lifting styles, there remains a lack of understanding of whole body kinematics during unrestricted lifting. The current study evaluated nine males and nine females while lifting two box weights (9.1 kg, 18.2 kg) from five origins below the waist (0, 19, 38, 57, and 76 cm above the floor) and from three task asymmetries (sagittally symmetric, 45° clockwise, 45° counter-clockwise). While the lifting style was significantly influenced by the height of lift origin and to a lesser extent gender, box weight, and task asymmetry, none of the conditions resulted in pure squat or stoop lifting style. However, for lifts above knee height, the lifting style resembled more of a stoop lift while lifts originating below knee height were more of a squat lift. As the origin moved closer to the floor, participants relied more on their hips to accomplish the sagittal flexion but overall adopted a more coordinated whole-body lifting style. All together, as more sagittal flexion is required, more joints are relied upon in a more coordinated effort. The current study indicates that caution needs to be exercised when applying results of pure squat or pure stoop lifting studies to free-style (realistic) lifting. [ABSTRACT FROM AUTHOR]

Any voluntary motion of the body causes an internal perturbation of balance. Load transfer during manual material handling may increase these perturbations. This study investigates effects of stance condition on postural control during lifting. Nineteen healthy subjects repeatedly lifted and lowered a load between a desk and a shelf. The base of support was varied between parallel and step stance. Ground reaction force and segmental kinematics were measured. Load transfer during lifting perturbed balance. In parallel stance postural response consisted of axial movements in the sagittal plane. Such strategy was accompanied by increased posterior shear forces after lift-off. Lifting in step stance provided extended support in anterior/posterior direction. The postural control mechanisms in the sagittal plane are less complex as compared to parallel stance. However, lifting in step stance was asymmetrical and thus accompanied by distinct lateral transfer of the body. Lateral shear forces were larger as compared to parallel stance. Both lifting techniques exhibit positive and negative aspects. We cannot recommend either one as being better in terms of postural control. [Copyright &y& Elsevier]

High physical work demands increase the risk of musculoskeletal disorders and sickness absence. Supermarket work involves a high amount of manual material handling. Identifying specific ergonomic risk factors is an important part of occupational health and safety efforts in the supermarket sector. In this cross-sectional field study among 64 supermarket workers, we used electromyography during the workday to determine the influence of lifting height and load mass on muscular workload of the low-back and neck/shoulder muscles during un-restricted manual material handling (grocery stocking). We found a significant effect of load mass, i.e., higher loads associated with higher muscular workload in the low-back and neck/shoulder muscles. We demonstrated a significant interaction between start and end position, i.e., lifts performed from 'Low' start positions to 'High' end positions demonstrated the highest low-back muscular workload, whereas 'High' positions were associated with increased neck/shoulder workload. In conclusion, lifting higher loads and lifting goods from low to high positions (low-back) and at high positions (neck/shoulder) are associated with higher muscular workload. These results can be used to guide highly warranted preventive initiatives to reduce the physical workload during supermarket work.

The aim of this study was to investigate the psychophysical infrequent lifting capacity (maximum acceptable weight of lift, MAWL) for a Chinese population. A nested-factorial experimental design with a participant factor nested within gender was employed. Forty-one Chinese participants (29 males, 12 females) participated in the study. Two frequencies (one lift every 8 h and one lift every 5 min) and six lifting heights (floor to knuckle, floor to shoulder, floor to reach, knuckle to shoulder, knuckle to reach, shoulder to reach) were evaluated. The results are compared with prior studies and they lead to the following conclusions. (1) The MAWLs were significantly affected by both the lifting frequency and lifting height. For lifting frequency, the MAWLs decreased markedly by nearly 30% from one lift every 8 h to one lift every 5 min. For lifting height, the MAWLs of the F-K was the greatest of all six lifting heights, followed by F-S, K-S, F-R, K-R and S-R was the smallest. (2) The MAWLs for Chinese females are significantly lower, but proportionately similar, to the MAWLs for Chinese males. (3) The Chinese participants had smaller capacities compared with the Occidental participants, and the rate of decrease in MAWL for the Chinese participants was much sharper than that of Occidental participants. (4) The MAWL of Chinese females was about 54 - 58% of the Chinese males, it is somewhat lower than those of 60 - 70% of the Occidental participants. [ABSTRACT FROM AUTHOR]

Spinal compression tolerance limits (SCTL) have been widely used by ergonomists in setting work tolerance limits for manual materials handling (MMH) operations. Thus, the effect of personal and experimental factors on spinal compression tolerance limits (SCTL) is reviewed with the aid of regression and correlation analyses performed on data compiled from the published literature. Tables of SCTL from various sources utilizing large number of specimens and personal factors are presented so that they can be accessed by ergonomists easily. Integrated biomechanical guidelines based on SCTL are provided for the design of MMH operations in the workplace. It is suggested that, in order to reduce the probability of MMH injuries, biomechanical tolerance limits should be set at the damage load instead of the load at fracture. The damage load is the weight which causes the first gross signs of damage such as tissue fluid and blood. An algorithm is described to demonstrate the use of a biomechanics approach to the design of MMH operations. [ABSTRACT FROM PUBLISHER]

The effect of time on an individual's lifting capacity over extended periods using a psychophysical approach was studied. Twelve male subjects estimated their lifting capacity in a 25 min period, and then attempted to lift this weight for an 8 h period under varying conditions. For one experimental condition the subjects were allowed to adjust the weight, the final adjusted maximum acceptable weight of lift (MAWOL) averaged 85·4% of the original MAWOL determined in the 25 min session. The subjects also attempted to lift for an 8 h period, without any weight adjustments. All 12 subjects lasted the 8 h at 2 lifts per min, but at a frequency of 8 lifts per min only three subjects completed the eight hour lifting task. This indicates that the psychophysical approach is a valid method to measure lifting capacity across the lower Hfting frequency range but overestimates the lifting capacity at the higher frequency range. Slight fluctuations were noted in heart rate and oxygen consumption which were recorded every hour. [ABSTRACT FROM PUBLISHER]

A field study was conducted to assess cardiorespiratory and musculoskeletal stress and strain and work output during manual sorting of postal parcels, and to detect the effects of parcel sorting on the maximal muscle strength and endurance. The volunteer subjects comprised 32 healthy male sorters with mean (± s.d.) age of 34 ± 7 years at five different sorting sites. Each subject was studied during one evening work shift. During the shift of 391 ± 46 min the subjects manually sorted 1173 ± 630 parcels and walked 4·7 ± 2·3 km with and without the load. While sorting, heart rate was 101 ±18 beats min−1. In the heaviest tasks the oxygen consumption was 1·2 ± 0·41 min−1, and no elevated blood lactate concentrations were found. Work postures in which the back was bent forward averaged 24% of the time for sorting. The overall cardiorespiratory rating and local ratings of perceived exertion for arms, back, and legs did not exceed the ‘somewhat strong’ level during the work shift. The maximal static strength both for the right and left hand-grip muscles was, on average, 3% lower (p<0·05) after the work shift than before the shift. No significant differences were found in the static or dynamic endurance times for the hand-grip muscles when the results obtained after the work shift were compared to the baseline values. At sorting centres the stress and strain on the cardiorespiratory and musculoskeletal system was evaluated to remain within acceptable limits for healthy male sorters. [ABSTRACT FROM PUBLISHER]

Slipping risk associated with manual material handling on inclined surfaces was investigated using a 24 factorial experimental design under controlled laboratory conditions. The reaction force data at the shoe sole-sloping surface interface, the box trajectories, and the subjects’ assessment of the risk involved in carrying out the prescribed tasks were obtained and analysed both analytically and statistically. The results of these analyses are presented in this paper. [ABSTRACT FROM PUBLISHER]

Manual material handling (MMH) is considered as one of the main contributors to low back pain. While males traditionally perform MMH tasks, recently the number of females who undertake these physically-demanding activities is also increasing. To evaluate the risk of mechanical injuries, the majority of previous studies have estimated spinal forces using different modeling approaches that mostly focus on male individuals. Notable sex-dependent differences have, however, been reported in torso muscle strength and anatomy, segmental mass distribution, as well as lifting strategy during MMH. Therefore, this study aimed to use sex-specific models to estimate lumbar spinal and muscle forces during static MHH tasks in 10 healthy males and 10 females. Motion-capture, surface electromyographic from select trunk muscles, and ground reaction force data were simultaneously collected while subjects performed twelve symmetric and asymmetric static lifting (10 kg) tasks. AnyBody Modeling System was used to develop base-models (subject-specific segmental length, muscle architecture, and kinematics data) for both sexes. For females, female-specific models were also developed by taking into account for the female's muscle physiological cross-sectional areas, segmental mass distributions, and body fat percentage. Males showed higher absolute L5-S1 compressive and shear loads as compared to both female base-models (25.3% compressive and 14% shear) and female-specific models (41% compressive and 23.6% shear). When the predicted spine loads were normalized to subjects' body weight, however, female base-models showed larger loads (9% compressive and 16.2% shear on average), and female-specific models showed 2.4% smaller and 9.4% larger loads than males. Females showed larger forces in oblique abdominal muscles during both symmetric and asymmetric lifting tasks, while males had larger back extensor muscle forces during symmetric lifting tasks. A stronger correlation between measured and predicted muscle activities was found in females than males. Results indicate that female-specific characteristics affect the predicted spinal loads and must be considered in musculoskeletal models. Neglecting sex-specific parameters in these models could lead to the overestimation of spinal loads in females., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Firouzabadi, Arjmand, Pan, Zander and Schmidt.)

The use of inertial measurement units (IMUs) for monitoring and classifying physical activities has received substantial attention in recent years, both in occupational and non-occupational contexts. However, a "user-friendly" approach is needed to promote this approach to quantify physical demands in actual workplaces. We explored the use of a single IMU for extracting information about different manual material handling (MMH) tasks (i.e., specific type of task performed, and associated duration and frequency), using a bidirectional long short-term memory network for classification. Classification performance using single IMUs placed on several body parts was compared with performance using multiple IMU configurations (2, 3, and 17 IMUs). Overall, the use of a single sensor led to satisfactory results (e.g., median accuracy >97%) in classifying MMH tasks and estimating task duration and frequency. Limited benefits were obtained using additional sensors, and several sensor locations yielded similar outcomes. Classification performance, though, was relatively inferior for push/pull vs. other tasks. [ABSTRACT FROM AUTHOR]

Work-related low back disorders are commonly associated with handling tasks. The objective of this study was to determine the combined influence of distance, pace, handled mass and height, on back loading and posture during free box transfer. Kinematics and kinetics of 17 handlers were recorded during a box transfer task between two pallets. Four-way repeated measures ANOVA were conducted on four lift-deposit height conditions (from lift and deposit of 0.16 or 1.16 m), three distances between pallets (1.5, 1.0 and 0.5 m), two handled masses (10 and 20 kg) and two paces (free and faster). The interaction between distance and height on back loading and posture (P < 0.001) showed that increasing distance to more than 1 m is not recommended to avoid unnecessary cumulative loading. The shorter distance of 0.5 m, which generally reduced the most spine loading, may increase it for transfers varying in height. The effect of pace to reduce spine cumulative loading and increase the peak asymmetric loading (P < 0.05) was accentuated by mass, height and distance. The combined factors revealed the importance of tradeoff between peak, cumulative and asymmetric loading. [ABSTRACT FROM AUTHOR]

OCCUPATIONAL APPLICATIONSBiomechanical risk factors associated with spacesuit manual material handling tasks were evaluated using the singular value decomposition (SVD) technique. SVD analysis decomposed each lifting tasks into primitive motion patterns called eigenposture progression (EP) that contributed to the overall task. Biomechanical metrics, such as total joint displacement, were calculated for each EP. The first EP (a simultaneous knee, hip, and waist movement) had greater biomechanical demands than other EPs. Thus, tasks such as lifting from the floor were identified as "riskier" by having a greater composition of the first EP. The results of this work can be used to improve a task as well as spacesuit design by minimizing riskier movement patterns as shown in this case study. This methodology can be applied in civilian occupational settings to analyze open-ended tasks (e.g., complex product assembly and construction) for ergonomics assessments. Using this method, worker task strategies can be evaluated quantitatively, compared, and redesigned when necessary.

OCCUPATIONAL APPLICATIONSWe present a practical method for minimizing low-back cumulative loading that leverages digital human modeling capabilities and optimization using an evolutionary algorithm. We demonstrate use of the method in a simulated lifting task. Our results show that this method is robust to different routines for calculating cumulative loading. The proposed method can aid ergonomics engineers in addressing a potential risk factor early in the design stage, even in the absence of an established threshold limit value, and it provides a time saving by eliminating the need to adjust workplace parameters across many design possibilities.

The aim of this study is to assess and reduce the risk due to manual material handling in a company involved in the foodstuff retailing. The risk assessment was performed by NIOSH Variable Lifing Index in 13 different occupational conditions. As result the risk was present in any case, with VLI values ranging from 2.12 to 2.81. A good risk reduction has been accomplished correcting properly the most important multiplier involved in the computation of the revised NIOSH Lifting equation (lifting frequency and weight of heavier products). Even if the performed risk reduction has been significant, the residual risk is still higher than the level of acceptability. [ABSTRACT FROM AUTHOR]