| 1. |
- Elcadi, Guilherme H.
(författare)
-
Near infrared spectroscopy for assessing oxygenation and hemodynamics in the upper extremities of healthy subjects and patients with work-related muscle pain
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The prevalence of work-related muscle pain (WRMP) is large in the general population in the industrialized world. Despite significant advances over recent years in some research areas, the mechanisms of why WRMP occurs and the pathophysiological mechanisms behind the disorders are still unclear. One suggested explanation is that WRMP is caused initially by a limitation of the local muscle circulation and oxidative metabolism. There is a lack of objective methods to gauge the development and diagnosis of WRMP. Near infrared spectroscopy (NIRS) is a non-invasive technique that allows for determinations of oxygenation and blood flow. The purpose of this thesis was to evaluate NIRS (1) as a method for measuring muscle oxygenation and hemodynamics for the extensor carpi radialis (ECR) and trapezius descendens muscles (TD), and (2) to investigate whether variables measured by NIRS differed between patients diagnosed with WRMP and healthy subjects. Several variables of NIRS were produced and investigated. These included muscle oxygenation (StO2%), changes during contractions (∆StO2%) and StO2% recovery (Rslope), total hemoglobin (HbT) as an indication of blood volume and its changes during contractions (∆HbT). In addition, for the ECR, by applying an upper arm venous occlusion (VO) HbTslope increase as a surrogate of blood flow, and for both VO and arterial occlusion (AO) HHbslope increase (i.e. deoxyhemoglobin slope) as a surrogate of oxygen consumption were variables of interest. A first objective was to determine how StO2% and HbT responded to various contraction forces and how it related to muscle activation measured by electromyography (EMG). For both muscles isometric contractions of 10, 30, 50 and 70% of maximal voluntary contraction (MVC) were maintained for 20 s each by healthy males and females; additionally a 10% MVC contraction was sustained for 5 min. For the different contraction levels, predictable relationships were seen between ∆StO2% and force, and between ∆StO2% and EMG RMS amplitude. The general trend was a decrease in ∆StO2% with increasing force and increasing EMG. Females showed a tendency for a higher oxygen use (i.e., drop in StO2%) for the ECR over force levels than males and a higher RMS% MVC for the TD. For the 10% MVC contraction sustained for 5 min gender specific changes over time for HbT and RMS for the ECR, and for StO2% for the TD muscle were seen. A second objective was to determine the day-to-day reliability of NIRS variables for the ECR and TD muscles at group level (Pooled data) and at gender level (males and females). Measurements were performed on two occasions separated by 4-6 days and intraclass correlation coefficients (ICC) and limits of agreement (LOA) were determined as reliability and reproducibility indicators, respectively. Variables tested were ∆StO2% during submaximal isometric contractions of 10, 30, 50 and 70% MVC and StO2% recovery (Rslope) after contractions and after AO. For the ECR, HbTslope as an indication of blood flow (using VO) and HHbslope as a surrogate of oxygen consumption for both VO and AO were computed. For ∆StO2% for the ECR the highest ICC was at 30% MVC for both the pooled data and at gender level. For the TD ICCs were comparably high for 30, 50, 70 % MVC (for both muscles the ∆StO2% at 10% MVC showed the lowest ICC). Further, females showed a higher ICC than males for contraction levels of 50 and 70% MVC. For both muscles, LOA for ∆StO2% was lowest at 10% and highest at 50 and 70% MVC. For the ECR Rslope ICCs were high for all contraction levels, but was lower for AO; LOA was lowest at 70% MVC. For the TD, Rslope ICCs were also high for all contraction levels and LOA was lowest at 30 % MVC. ICC for HbTslope was the lowest of all variables tested. For HHbslope ICC was higher for AO than for VO, and LOA was lower for AO. A third objective was to determine if there were differences between healthy subjects and patients diagnosed with WRMP in ∆StO2% and ∆HbT responses during varying submaximal contractions (10, 30, 50 and 70% MVC), and StO2% recovery (Rslope) immediately after contractions and AO. Additional variables tested in the ECR at rest were HHbslope to indicate oxygen consumption (using AO) and HbTslope as an indication of blood flow. There were no differences between groups in ∆StO2% and ∆HbT variables during the contractions or Rslope in the recovery after contractions or AO. Furthermore, HbTslope was not different between groups However, oxygen consumption for the ECR and StO2% for the TD at rest were significantly greater for healthy subjects compared to patients. A fourth objective was to determine if there were differences in StO2% and HbT between healthy subjects and WRMP patients during a 12 min sustained contraction of 15 % MVC. In addition, the protocol included a recovery period of 30 min. Prior to contraction, as well as during the recovery period, HbTslope as a surrogate of blood flow was determined for the ECR. Neither the ECR nor the TD exhibited significant differences between groups for StO2% and HbT during the contraction. For the TD patients showed a lower StO2% value at rest and throughout the contraction than healthy subjects. For the ECR HbT during the sustained contraction the general trend was an initial decrease with gradual increase throughout the contraction for both groups. For HbTslope no differences were seen between patients and healthy subjects before the sustained contraction and during the recovery period for both muscles.NIRS is deemed a suitable technique for assessing physiological measurements of the upper extremity, including for day-to-day testing.NIRS was not able to distinguish between the patients with WRMP and controls. A concern in the thesis is the characteristics of the patient group in being equally active in recreational sports, actively working, and similar in muscle strength as controls. Thus, applying NIRS for studying a more severe patient group could yield different results.
|
|
| 2. |
- Palm, Peter, 1975-
(författare)
-
Methods to assess physical load at work : With a focus on the neck and upper extremities
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To prevent work-related musculoskeletal disorders (MSDs), useful, reliable and valid methods for assessing physical workload and risks for MSDs are needed. Ergonomists often assess work by short visual observations without a specific tool. A branch-specific tool was developed for assessing working technique during cash register work (BAsiK observation protocol).Inclinometers are an alternative for assessing upper arm postures - over several days. Ergonomists need guidelines explaining how to analyze and interpret such data.The aim was to examine and investigate methods for assessing physical load at work, with focus on the neck and upper extremities.In Paper:I, the reliability and criterion validity of the BAsIK observation protocol were assessed.II, the reliability of risk assessments of repetitive work, based on visual observations performed by 21 ergonomists without a specific tool, was assessed.III, whole-day inclinometer measurements of upper arm elevation were compared between work and leisure, across 13 different occupations – before and after arm elevations during sitting time was excluded.IV, the association between inclinometer-based upper arm elevation and neck/shoulder pain was assessed among 654 blue-collar workers. The intra-observer reliability of the BAsIK protocol was deemed acceptable, but only 3 of 10 questions in the protocol showed acceptable inter-observer reliability, and 3 showed acceptable criterion validity.Neither the inter- or intra-observer reliability of risk assessment without any specific method was acceptable for any upper body regions.None of the occupation groups, in paper III, had higher proportion of time with arm elevation during work than leisure. However, when arm elevation during sitting was excluded, 8 occupation groups had higher proportion of time with elevated arms during work than leisure.Whole-workday inclinometer-based upper arm elevation was not associated with neck/shoulder pain within the assessed population. The results indicate that, in most cases, a single visual observation of a work sequence is not a reliable means of assessing repetitive work. A large proportion of arm elevation may derive from sitting time. At low exposure levels, arm elevation per se may not be a risk factor for neck/shoulder pain.This must be taken into account when evaluating the risk for MSDs.
|
|
| 3. |
|
|
| 4. |
- Yang, Liyun, 1992-
(författare)
-
Ergonomic Risk Assessment and Intervention through Smart Workwear Systems
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rapid development of wearable technology has provided opportunities to ergonomics research and practice with new ways for workload measurements, data analytics, risk assessment and intervention. This thesis aims at developing and evaluating methods using wearable technologies to assess physical risk factors at work, and further to give feedback to employees to improve their work techniques.One smartphone application (ErgoArmMeter) was developed for the assessment of upper arm postures and movements at work. The application uses integrated signals of the embedded accelerometer and gyroscope, and processes and presents the assessment results directly after a measurement. Laboratory validation with 10 participants was performed using an optical tracking system as standard measurement. The results showed that the application had similar accuracy compared to standard inclinometry for static postures and improved accuracy in dynamic conditions. With its convenience and low cost, the application may be used by researchers and practitioners in various scenarios for risk assessment.Three models for assessment of work metabolism (WM) using heart rate (HR) and accelerometers (ACCs) were evaluated during simulated work tasks with 12 participants against indirect calorimetry as standard measurement. The HR + arm-leg ACC model showed best accuracy in most work tasks. The HR-Flex model showed a small bias for the average of all tasks. For estimating WM in the field using wearable technologies, the HR-Flex model or the HR + arm-leg ACC model may be chosen depending on the need for accuracy level and resource availabilities. Further improvement of the classification algorithm in the HR + arm-leg ACC model is needed in order to suit various types of work.Two smart workwear systems were developed and evaluated. Smart workwear system 1.0 consisted of a sensorized vest, an inertial measurement unit (IMU) and an Android tablet application. It assessed risks of high physiological workload and prolonged occupational sitting/standing. The results were visualized by color-coded risk levels. The system was evaluated with 8 participants from four occupations in a field study. It was perceived as useful, comfortable and not disturbing by most participants. Further development is required for the system for automated risk assessment of various ergonomic risk factors in real work situations.Smart workwear system 2.0 consisted of an instrumented t-shirt with IMUs, vibration units and an Android smartphone application. It provided vibrotactile feedback to users’ upper arm and trunk when predefined angular thresholds were exceeded. The system was evaluated for work postures intervention in industrial order picking among 15 participants. It showed to be effective in improving the trunk and dominant upper arm postures. The system was perceived as comfortable and useful. The vibrotactile feedback was evaluated as supportive for learning regarding workplace and task design among the participants.In conclusion, the research in this thesis showed that wearable technologies can be used both in the laboratory and field for assessment of physical risk factors at work and intervention in work technique improvement. With further research and development, smart workwear systems may contribute to automated risk assessment, prevention of work-related ill health, and improvement of the design and overall quality of work.
|
|
| 5. |
- Zetterberg, Camilla, 1970-
(författare)
-
The impact of visually demanding near work on neck/shoulder discomfort and trapezius muscle activity : Laboratory studies
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Musculoskeletal discomfort in the neck and shoulders is common among workers performing visually demanding near work, e.g., on a computer screen, and sustained low-level muscle activity during such work can lead to work-related pain. The relationships between visual demands and muscle activity and discomfort in the neck/shoulder region are at present unclear. Aim: The aims of this thesis were to determine whether neck/shoulder discomfort and trapezius muscle activity increases during visually demanding experimental near work, and to investigate whether eye-lens accommodation is a mediating mechanism behind increased trapezius muscle activity. Methods: The four papers included are based on two experiments with different visually demanding near work tasks (duration 5 and 7 min). Trial lenses of different diopters were used to manipulate the visual demands (i.e., induce more or less accommodation) and thereby create different viewing conditions. Monocular viewing, which does not require active convergence, was used to examine the isolated effect of accommodation. Eye-lens accommodation and trapezius muscle activity were measured continuously during the visual tasks, and in one experiment the participants rated their eye and neck/shoulder discomfort at baseline and after each visual task. Results: Neck/shoulder discomfort and trapezius muscle activity increased during the visually demanding near work and participants experiencing a greater increase in eye discomfort (compared with baseline) also developed more neck/shoulder discomfort with time. There were no significant differences in muscle activity among the viewing conditions, and no effect of isolated accommodation response within the monocular viewing conditions. Conclusion: These findings indicate that accommodation per se is unlikely to mediate trapezius muscle activity. Instead, the increase in trapezius muscle activity observed here may be due to a combination of high visual attention and enhanced requirement for eye-neck (head) stabilisation. Since these results suggest that neck/shoulder discomfort may aggravate with time when the visual demands are high, it is important to provide good visual conditions in connection with visually demanding occupations.
|
|
| 6. |
- Eliasson, Kristina, 1979-
(författare)
-
Ergonomists’ risk assessments : From guesstimates to strategic approaches
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Musculoskeletal disorders are among the most prevalent causes of work-related ill-health, consequently risk assessments of hazardous factors related to these disorders are important for prevention. Occupational Health Services (OHS) providers are independent experts, supporting employers regarding work environment issues and rehabilitation. Ergonomists represents one of the professions within OHS, and risk assessment regarding musculoskeletal disorders is within the scope of their work tasks. The overall objective was to explore Swedish ergonomists’ practices and approaches with risk assessments, in order to contribute new knowledge about how ergonomists’ work methods can be further developed to improve prevention of work-related musculoskeletal disorders. Paper I explored the process of risk assessment assignments and the ergonomists’ use of observation-based risk-assessment tools. The result showed a lack of systematic approaches regarding risk assessment assignments and limited use and knowledge of observation-based risk-assessment tools. In Paper II inter-observer and intra-observer reliability of risk assessments, without the use of an explicit observational method were assessed. The results showed a non-acceptable reliability. Paper III explored ergonomists experiences of an e-learning concept for knowledge translation in the OHS context. The e-learning concept was considered as feasible. The knowledge translation inspired increased use of risk-assessment tools, changes in the risk assessment procedures, e.g. selection of tools, and employing a participatory approach. Paper IV described the development of a process model for occupational health surveillance for workers exposed to hand-intensive work (HIW-model), and the studies that will explore the model. Paper V explored company representatives’ experiences of the HIW-model, and factors which facilitated the execution of the model. The model contributed to increased risk awareness and understanding of how individual workers’ musculoskeletal ill-health relates to exposures in work. Facilitating factors were: a joint start-up meeting in which the process was planned, clear communication, and clarity regarding the ownership of the process. In conclusion, the findings showed that ergonomists’ expertise is needed in the entire risk management process and not only in the risk assessment phase. In this process, the ergonomists need to be active and take the expert role (which includes a stocked toolbox) and support the employer through the whole risk management process from initiation to evaluation of risk controlling measures.
|
|
| 7. |
- Eliasson, Kristina, 1979-
(författare)
-
Occupational health services in the prevention of musculoskeletal disorders : Processes, tools and organizational aspects
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Work-related musculoskeletal disorders are associated with high costs and it is essential to prevent them. Occupational Health Services(OHS) provide expert services regarding work environment, health and rehabilitation of work related disorders. Risk assessments of the work environment can be an initial step for preventive measures, and ergonomists can be assigned by clients to assess exposures in the work environment. For such assignments different tools can be used. The aim of this thesis was to explore prerequisites, processes and practices of OHS consultants in Sweden within the domain of primary prevention of work-related musculoskeletal disorders. This was explored through the work of ergonomists in their role of assessing ergonomics risks. The research methodology was both quantitative and qualitative. Data collection includes a web questionnaire, semi-structured interviews and inter- and intra-observer reliability tests. The results shows that ergonomics risk assessments were most commonly initiated reactively and a systematic work methodology for the risk assessment process was often lacking. Swedish ergonomists used only a few standardized tools for risk assessment. The Ergonomics provision from the Swedish Work Environment Authority, AFS-98, was widely used, but other observation-based tools were used far less often. Ergonomics risks were often assessed solely by means of observation, based on ergonomists’ knowledge and experience. The results also pointed to that that the reliability was not acceptable when risk assessment was performed without any standardized tool. Furthermore, the results point to that support from the OHS organizations is an important prerequisite for ergonomists to work with primary prevention. Further, opportunities for specialization within a specific industry sector seem to facilitate ergonomic interventions. It is also important to have close relationships with clients and to make them aware about ergonomists competence. Conclusively, this thesis identifies a numbers of areas in which OHS must develop to improve primary preventive services regarding work environment.
|
|
| 8. |
- Fan, Xuelong, et al.
(författare)
-
Effects of sensor types and angular velocity computational methods in field measurements of occupational upper arm and trunk postures and movements
- 2021
-
Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 21:16
-
Tidskriftsartikel (refereegranskat)abstract
- Accelerometer-based inclinometers have dominated kinematic measurements in previous field studies, while the use of inertial measurement units that additionally include gyroscopes is rapidly increasing. Recent laboratory studies suggest that these two sensor types and the two commonly used angular velocity computational methods may produce substantially different results. The aim of this study was, therefore, to evaluate the effects of sensor types and angular velocity computational methods on the measures of work postures and movements in a real occupational setting. Half-workday recordings of arm and trunk postures, and movements from 38 warehouse workers were compared using two sensor types: accelerometers versus accelerometers with gyroscopes—and using two angular velocity computational methods, i.e., inclination velocity versus generalized velocity. The results showed an overall small difference (<2° and value independent) for posture percentiles between the two sensor types, but substantial differences in movement percentiles both between the sensor types and between the angular computational methods. For example, the group mean of the 50th percentiles were for accelerometers: 71°/s (generalized velocity) and 33°/s (inclination velocity)—and for accelerometers with gyroscopes: 31°/s (generalized velocity) and 16°/s (inclination velocity). The significant effects of sensor types and angular computational methods on angular velocity measures in field work are important in inter-study comparisons and in comparisons to recommended threshold limit values.
|
|
| 9. |
- Forsman, Mikael, Professor, et al.
(författare)
-
Mind the gap – development of conversion models between accelerometer- and IMU-based measurements of arm and trunk postures and movements in warehouse work
- 2022
-
Ingår i: Applied Ergonomics. - : Elsevier BV. - 0003-6870 .- 1872-9126. ; 105
-
Tidskriftsartikel (refereegranskat)abstract
- Sensor type (accelerometers only versus inertial measurement units, IMUs) and angular velocity computational method (inclination versus generalized velocity) have been shown to affect the measurements of arm and trunk movements. This study developed models for conversions between accelerometer and IMU measurements of arm and trunk inclination and between accelerometer and IMU measurements of inclination and generalized (arm) velocities. Full-workday recordings from accelerometers and IMUs of arm and trunk postures and movements from 38 warehouse workers were used to develop 4 angular (posture) and 24 angular velocity (movement) conversion models for the distributions of the data. A power function with one coefficient and one exponent was used, and it correlated well (r2 > 0.999) in all cases to the average curves comparing one measurement with another. These conversion models facilitate the comparison and merging of measurements of arm and trunk movements collected using the two sensor types and the two computational methods.
|
|
| 10. |
- Lind, Carl Mikael, et al.
(författare)
-
Wearable Motion Capture Devices for the Prevention of Work-Related Musculoskeletal Disorders in Ergonomics-An Overview of Current Applications, Challenges, and Future Opportunities
- 2023
-
Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 23:9
-
Forskningsöversikt (refereegranskat)abstract
- Work-related musculoskeletal disorders (WMSDs) are a major contributor to disability worldwide and substantial societal costs. The use of wearable motion capture instruments has a role in preventing WMSDs by contributing to improvements in exposure and risk assessment and potentially improved effectiveness in work technique training. Given the versatile potential for wearables, this article aims to provide an overview of their application related to the prevention of WMSDs of the trunk and upper limbs and discusses challenges for the technology to support prevention measures and future opportunities, including future research needs. The relevant literature was identified from a screening of recent systematic literature reviews and overviews, and more recent studies were identified by a literature search using the Web of Science platform. Wearable technology enables continuous measurements of multiple body segments of superior accuracy and precision compared to observational tools. The technology also enables real-time visualization of exposures, automatic analyses, and real-time feedback to the user. While miniaturization and improved usability and wearability can expand the use also to more occupational settings and increase use among occupational safety and health practitioners, several fundamental challenges remain to be resolved. The future opportunities of increased usage of wearable motion capture devices for the prevention of work-related musculoskeletal disorders may require more international collaborations for creating common standards for measurements, analyses, and exposure metrics, which can be related to epidemiologically based risk categories for work-related musculoskeletal disorders.
|
|
