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Yang W, Wang H, He R. Establishment of a finite element model based on craniofacial soft tissue thickness measurements and stress analysis of medical goggles. ERGONOMICS 2022; 65:305-326. [PMID: 34304717 DOI: 10.1080/00140139.2021.1961023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 07/22/2021] [Indexed: 06/13/2023]
Abstract
In this study, an accurate finite element (FE) stress analysis of head-mounted products for Chinese users was performed. Using craniofacial computed tomography scans of 280 Chinese individuals, the total soft tissue thickness and thickness of the fat and muscle layers for 41 landmarks were measured. The data were used to construct FE head models (FEH). An FE stress test was conducted to analyse the wearing of medical goggles using two FE models based on one-layer (FEH 1) and three-layer (FEH 3) soft tissue material parameters. When compared with the experimental results, the modelling results for FEH 3 were more realistic than those for FEH 1. Wearing medical goggles led to stress concentration over five landmark areas, A: upper medial forehead, B: temporal, C: zygion, D: infraorbital fossa and E: rhinion, of which B, C and D caused the most discomfort during long-term goggle wear. Practitioner summary: A precise FE head model can reflect the complex contact pressure of a head-related product. Two FE models based on one- and three-layer soft tissue material parameters were established and tested separately with medical goggles. The model can be used to improve the comfort of head-related products. Abbreviations: FE: finite element; FEH: FE head models; FEH 1: FE models based on one-layer; FEH 3: FE models based on three-layer; VR: virtual reality; AR: augmented reality; 3D: three-dimensional; WSU: Wayne State University; WSUBIM: Wayne State University Brain Injury Model; CT: computed tomography; MRI: magnetic resonance imaging; CFSTT: craniofacial soft tissue thickness; FSR: force sensing resistor; NURBS: non-uniform rational basis spline; SPSS: statistical product and service solutions; STL: stereolithography; STP: standard for the exchange of product model data; BDF: glyph bitmap distribution format; EEG: electroencephalogram.
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Affiliation(s)
- Wenxiu Yang
- School of Design, Hunan University, Changsha, China
| | - Haining Wang
- School of Design, Hunan University, Changsha, China
| | - Renke He
- School of Design, Hunan University, Changsha, China
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Skals S, Bláfoss R, de Zee M, Andersen LL, Andersen MS. Effects of load mass and position on the dynamic loading of the knees, shoulders and lumbar spine during lifting: a musculoskeletal modelling approach. APPLIED ERGONOMICS 2021; 96:103491. [PMID: 34126573 DOI: 10.1016/j.apergo.2021.103491] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 05/27/2021] [Accepted: 06/02/2021] [Indexed: 06/12/2023]
Abstract
Musculoskeletal models may enhance our understanding of the dynamic loading of the joints during manual material handling. This study used state-of-the-art musculoskeletal models to determine the effects of load mass, asymmetry angle, horizontal location and deposit height on the dynamic loading of the knees, shoulders and lumbar spine during lifting. Recommended weight limits and lifting indices were also calculated using the NIOSH lifting equation. Based on 1832 lifts from 22 subjects, we found that load mass had the most substantial effect on L5-S1 compression. Increments in asymmetry led to large increases in mediolateral shear, while load mass and asymmetry had significant effects on anteroposterior shear. Increased deposit height led to higher shoulder forces, while the horizontal location mostly affected the forces in the knees and shoulders. These results generally support the findings of previous research, but notable differences in the trends and magnitudes of the estimated forces were observed.
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Affiliation(s)
- Sebastian Skals
- Musculoskeletal Disorders and Physical Workload, National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen East, Denmark; Sport Sciences - Performance and Technology, Department of Health Science and Technology, Aalborg University, Niels Jernes Vej 12, 9220 Aalborg East, Denmark.
| | - Rúni Bláfoss
- Musculoskeletal Disorders and Physical Workload, National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen East, Denmark; Research Unit for Muscle Physiology and Biomechanics, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
| | - Mark de Zee
- Sport Sciences - Performance and Technology, Department of Health Science and Technology, Aalborg University, Niels Jernes Vej 12, 9220 Aalborg East, Denmark.
| | - Lars Louis Andersen
- Musculoskeletal Disorders and Physical Workload, National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen East, Denmark; Sport Sciences - Performance and Technology, Department of Health Science and Technology, Aalborg University, Niels Jernes Vej 12, 9220 Aalborg East, Denmark.
| | - Michael Skipper Andersen
- Department of Materials and Production, Aalborg University, Fibigerstræde 16, 9220 Aalborg, Denmark.
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Liu B, Ma L, Chen C, Zhang Z. Experimental validation of a subject-specific maximum endurance time model. ERGONOMICS 2018; 61:806-817. [PMID: 29224501 DOI: 10.1080/00140139.2017.1416180] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 12/07/2017] [Indexed: 06/07/2023]
Abstract
This study aimed at experimentally validating a subject-specific maximum endurance time (MET) model. Thirty health participants (15 males and 15 females; Age: mean = 21.5 years, SD = 1.6 years) volunteered to conduct an isometric elbow flexion task until exhaustion. The endurance times of each participant were measured under relative exertion levels ranging from 30% MVC (Maximum Voluntary Contraction) to 70% MVC at 10% intervals. Assessment of the model showed that the intensity-endurance time relationship for each studied individual could be well fitted by the subject-specific MET model (R2 > 0.89). The fatigue rates identified from the model fitting were normally distributed (Mean = 0.96 min-1, SD = 0.29 min-1). In addition, the fatigue rates of the male group were significantly higher than the female group. The subject-specific MET model can be used to predict the MET for individual workers, and further support physical task design, based on the fatigability data of a targeted worker population. Practitioner Summary: Ergonomists have extensively used MET models in physical fatigue assessment and physical task design. A subject-specific MET model could be used to predict the MET at individual levels, and also to support work design for a target worker population, based on the fatigability data distribution obtained from sampled workers.
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Affiliation(s)
- Bin Liu
- a Department of Industrial Engineering , Tsinghua University , Beijing , China
| | - Liang Ma
- a Department of Industrial Engineering , Tsinghua University , Beijing , China
| | - Chi Chen
- a Department of Industrial Engineering , Tsinghua University , Beijing , China
| | - Zhanwu Zhang
- b Hon Hai Precision Industry (Zhengzhou) Co Ltd , Zhengzhou , China
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Doan J, Awosoga O, Provost T, Blinch J, Hudson J. Perceived affordances and postures for lifting in child care. THEORETICAL ISSUES IN ERGONOMICS SCIENCE 2017. [DOI: 10.1080/1463922x.2016.1214986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Jon Doan
- Engineering & Human Performance Lab, Department of Kinesiology & Physical Education, University of Lethbridge, Lethbridge, Canada
| | - Olu Awosoga
- Faculty of Health Sciences, University of Lethbridge, Lethbridge, Canada
| | - Trishell Provost
- Engineering & Human Performance Lab, Department of Kinesiology & Physical Education, University of Lethbridge, Lethbridge, Canada
| | - Jarrod Blinch
- Engineering & Human Performance Lab, Department of Kinesiology & Physical Education, University of Lethbridge, Lethbridge, Canada
| | - Jessica Hudson
- Faculty of Health Sciences, University of Lethbridge, Lethbridge, Canada
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Bazrgari B, Xia T. Application of advanced biomechanical methods in studying low back pain - recent development in estimation of lower back loads and large-array surface electromyography and findings. J Pain Res 2017; 10:1677-1685. [PMID: 28761372 PMCID: PMC5522670 DOI: 10.2147/jpr.s139185] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Low back pain (LBP) is a major public health problem and the leading disabling musculoskeletal disorder globally. A number of biomechanical methods using kinematic, kinetic and/or neuromuscular approaches have been used to study LBP. In this narrative review, we report recent developments in two biomechanical methods: estimation of lower back loads and large-array surface electromyography (LA-SEMG) and the findings associated with LBP. The ability to estimate lower back loads is very important for the prevention and the management of work-related low back injuries based on the mechanical loading model as one category of LBP classification. The methods used for estimation of lower back loads vary from simple rigid link-segment models to sophisticated, optimization-based finite element models. In general, reviewed reports of differences in mechanical loads experienced in lower back tissues between patients with LBP and asymptomatic individuals are not consistent. Such lack of consistency is primarily due to differences in activities under which lower back mechanical loads were investigated as well as heterogeneity of patient populations. The ability to examine trunk neuromuscular behavior is particularly relevant to the motor control model, another category of LBP classification. LA-SEMG not only is noninvasive but also provides spatial resolution within and across muscle groups. Studies using LA-SEMG showed that healthy individuals exhibit highly organized, symmetric back muscle activity patterns, suggesting an orderly recruitment of muscle fibers. In contrast, back muscle activity patterns in LBP patients are asymmetric or multifocal, suggesting lack of orderly muscle recruitment. LA-SEMG was also shown capable of capturing unique back muscle response to manual therapy. In conclusion, estimation of low back load and LA-SEMG techniques demonstrated promising potentials for understanding LBP and treatment effects. Future studies are warranted to fully establish clinical validity of these two biomechanical methods.
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Affiliation(s)
- Babak Bazrgari
- F. Joseph Halcomb III, M.D. Department of Biomedical Engineering, University of Kentucky, Lexington, KY
| | - Ting Xia
- Palmer Center for Chiropractic Research, Palmer College of Chiropractic, Davenport, IA, USA
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Coenen P, Kingma I, Boot CRL, Bongers PM, van Dieën JH. Detailed assessment of low-back loads may not be worth the effort: A comparison of two methods for exposure-outcome assessment of low-back pain. APPLIED ERGONOMICS 2015; 51:322-330. [PMID: 26154229 DOI: 10.1016/j.apergo.2015.06.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 04/12/2015] [Accepted: 06/04/2015] [Indexed: 06/04/2023]
Abstract
The trade-off between feasibility and accuracy of measurements of physical exposure at the workplace has often been discussed, but is unsufficiently understood. We therefore explored the effect of two low-back loading measurement tools with different accuracies on exposure estimates and their associations with low-back pain (LBP). Low-back moments of 93 workers were obtained using two methods: a moderately accurate observation-based method and a relatively more accurate video-analysis method. Group-based exposure metrics were assigned to a total of 1131 workers who reported on their LBP status during three follow-up years. The two methods were compared regarding individual and group-based moments and their predictive value for LBP. Differences between the two methods for peak moments were high at the individual level and remained substantial at group level. For cumulative moments, differences between the two methods were attenuated as random inaccuracies cancelled out. Peak moments were not predictive for LBP in any method while cumulative moments were, suggesting comparable predictive values of the two methods. While assessment of low-back load improves from investing in collecting relatively more accurate individual-based data, this does not necessarily lead to better predictive values on a group level, especially not for cumulative loads.
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Affiliation(s)
- Pieter Coenen
- School of Physiotherapy and Exercise Science, Curtin University, Perth, WA, Australia; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands; Body@Work, Research Center on Physical Activity, Work and Health, The Netherlands
| | - Idsart Kingma
- MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands; Body@Work, Research Center on Physical Activity, Work and Health, The Netherlands
| | - Cécile R L Boot
- Body@Work, Research Center on Physical Activity, Work and Health, The Netherlands; Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Paulien M Bongers
- Body@Work, Research Center on Physical Activity, Work and Health, The Netherlands; TNO Healthy Living, Hoofddorp, The Netherlands
| | - Jaap H van Dieën
- MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands; Body@Work, Research Center on Physical Activity, Work and Health, The Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.
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Coenen P, Kingma I, Boot CRL, Bongers PM, van Dieën JH. Cumulative mechanical low-back load at work is a determinant of low-back pain. Occup Environ Med 2014; 71:332-7. [PMID: 24676271 DOI: 10.1136/oemed-2013-101862] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES Reported associations of physical exposures during work (eg, lifting, trunk flexion or rotation) and low-back pain (LBP) are rather inconsistent. Mechanical back loads (eg, moments on the low back) as a result of exposure to abovementioned risk factors have been suggested to be important as such loads provide a more direct relationship with tissue failure and thus LBP. Since information on the effect of such load metrics with LBP is lacking yet, we aimed to assess this effect in a prospective study. METHODS Of 1131 workers, categorised into 19 groups, LBP was prospectively assessed over 3 years. Video and hand force recordings of 4-5 workers per group (93 in total) were used to estimate mechanical low-back loads (peak load and three cumulative load metrics, ie, linear weighted load, squared weighted load and load weighted to the tenth power) during manual materials handling (MMH) tasks using a video analysis method. These data were combined with static mechanical load estimates based on structured observation of non-MMH tasks. Associations of mechanical loads and LBP were tested using generalised estimating equations. RESULTS Significant effects on LBP were found for cumulative low-back moments (linear and squared weighted; both p<0.01 and ORs of 3.01 and 3.50, respectively) but not for peak and cumulative moments weighted to the tenth power. CONCLUSIONS Results of this first prospective study on the effect of mechanical low-back load on LBP support a LBP aetiology model of cumulative loads, potentially due to accumulation of microdamage or fatigue. Therefore, prevention of LBP should focus on reducing cumulative low-back loads, especially in highly exposed occupational groups, for example, by reducing handling of heavy loads and working in awkward body postures.
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Affiliation(s)
- Pieter Coenen
- MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands
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Poplin GS, Roe DJ, Peate W, Harris RB, Burgess JL. The association of aerobic fitness with injuries in the fire service. Am J Epidemiol 2014; 179:149-55. [PMID: 24186973 DOI: 10.1093/aje/kwt213] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The aim of the present study was to understand the risk of injury in relation to fitness in a retrospective occupational cohort of firefighters in Tucson, Arizona, from 2005 to 2009. Annual medical evaluations and injury surveillance data were linked to compare levels of aerobic fitness in injured employees with those in noninjured employees. The individual outcomes evaluated included all injuries, exercise-related injuries, and sprains and strains. Time-to-event analyses were conducted to determine the association between levels of fitness and injury likelihood. Fitness, defined by relative aerobic capacity (Vo2max), was associated with injury risk. Persons in the lowest fitness level category (Vo2max <43 mL/kg/minute) were 2.2 times more likely (95% confidence interval: 1.72, 2.88) to sustain injury than were those in the highest fitness level category (Vo2max >48 mL/kg/minute). Those with a Vo2max between 43 and 48 mL/kg/minute were 1.38 times (95% confidence interval: 1.06, 1.78) more likely to incur injury. Hazard ratios were found to be greater for sprains and strains. Our results suggest that improving relative aerobic capacity by 1 metabolic equivalent of task (approximately 3.5 mL/kg/minute) reduces the risk of any injury by 14%. These findings illustrate the importance of fitness in reducing the risk of injury in physically demanding occupations, such as the fire service, and support the need to provide dedicated resources for structured fitness programming and the promotion of injury prevention strategies to people in those fields.
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Ma L, Zhang W, Hu B, Chablat D, Bennis F, Guillaume F. Determination of subject-specific muscle fatigue rates under static fatiguing operations. ERGONOMICS 2013; 56:1889-1900. [PMID: 24192336 DOI: 10.1080/00140139.2013.851283] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Cumulative local muscle fatigue may lead to potential musculoskeletal disorder (MSD) risks, and subject-specific muscle fatigability needs to be considered to reduce potential MSD risks. This study was conducted to determine local muscle fatigue rate at shoulder joint level based on an exponential function derived from a muscle fatigue model. Forty male subjects participated in a fatiguing operation under a static posture with a range of relative force levels (14-33%). Maximum muscle strengths over time were measured after different fatiguing sessions. The time course of strength decline was fitted to the exponential function. Subject-specific fatigue rates of shoulder joint moment strength were determined. Good correspondence ([Formula: see text]) was found in the regression of the majority (35 out of 40 subjects). Substantial inter-individual variability in fatigue rate was found and discussed.
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Affiliation(s)
- Liang Ma
- a Department of Industrial Engineering , Tsinghua University , 100084 , Beijing , P.R. China
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Xiong S, Goonetilleke RS, Jiang Z. Pressure thresholds of the human foot: measurement reliability and effects of stimulus characteristics. ERGONOMICS 2011; 54:282-293. [PMID: 21390958 DOI: 10.1080/00140139.2011.552736] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Information related to reliable values of discomfort thresholds can help to improve the designs of various products. This study aimed to investigate the measurement reliabilities associated with pressure thresholds, while determining the effects of stimulus characteristics (stimulus area, indentation speed) of the human foot. An indentation apparatus was used with four sizes of indentation probes and three indentation speeds. In total, 13 locations on the right foot of 10 male and 10 female participants were tested to determine the pressure discomfort thresholds (PDT) and pressure pain thresholds (PPT). Results show that the tests had very good measurement reliability with intra-class correlations (ICC) greater than 0.8 for the PPT measurements and acceptable reliability (most ICC > 0.75, with a few between 0.5 and 0.75) for the PDT measurements, demonstrating that participants are capable of judging their pain and discomfort thresholds. Pressure sensitivity differs across locations of the foot, with the medial plantar arch of the foot being the most sensitive, followed by the dorsal surface of the foot. The heel area was the least sensitive. PPT and PDT are dependent on the stimulus characteristics of the area and the speed of indentation. A smaller area has a higher PPT and PDT, indicating significant effects of spatial summation. The increase of PDT and PPT at higher speeds may be partially explained by the increase in stiffness because foot tissue exhibits viscoelastic properties. The findings can have a significant impact on the design of footwear and other accessories for improved foot health and comfort. Statement of Relevance: This study investigated the threshold measurement reliability while determining the pressure sensitivity on the surface of the foot with varying stimulus characteristics. The findings may be very useful in the design of footwear and other accessories for improved comfort and reduced injuries.
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Affiliation(s)
- Shuping Xiong
- Department of Industrial Engineering and Management, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, Peoples Republic of China
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Abstract
Trunk kinematics variables have been shown to be related to low back injury risk during lifting tasks and it was hypothesised that changes in hand-hold positions could influence trunk kinematics and thereby risk. Fourteen subjects lifted a 5 or 10 kg box using four different hand placement locations (two symmetric and two asymmetric) while their trunk kinematics (position, velocity and acceleration in the sagittal, coronal and transverse planes) were captured using the lumbar motion monitor (LMM). These kinematics data were then used to calculate the probability of high risk group membership (PHRGM) as defined in the LMM risk assessment model. The results showed significant effects of hand placement on trunk kinematics, resulting in significant changes in the PHRGM variable ranging from a low of 20% in a the symmetric low load condition to a high of 38% under the asymmetric, 10 kg condition. STATEMENT OF RELEVANCE: Manual materials handlers use a variety of hand-hold positions on boxes during lifting. Where a lifter grabs the box can influence the trunk kinematics during the lifting task and these kinematics have been shown to provide some insight into risk of low back injury. This study documents the trunk postures and kinematics as a function of hand-hold position.
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Affiliation(s)
- Omid Haddad
- The Ergonomics Laboratory, Department of Industrial and Manufacturing Systems Engineering, Iowa State University, Ames, IA 50011-2164, USA
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