Work-related musculoskeletal disorders - exposure assessment and gender aspects

Work-related musculoskeletal disorders are widespread, and are, for unclear reasons, more common among females than in males. Several risk factors have been described; constrained and awkward postures, repetitive and/or force demanding motions, and lack of recovery. The exposure to such risk factors was systematically assessed in 116 male and 206 female fish-processing industry workers. Large differences were shown, females to a much higher extent performed repetitive work with constrained neck postures, while males had heavier, but more varied work tasks. Surface electromyography (EMG) was evaluated as a measurement method of muscular activity. An important aspect is time for recovery of muscle fibres, especially in work tasks that demand low level, long duration activity. Muscle fibres are recruited according to a predefined order, some them, probably, being active whenever the muscle is used. To assess recovery time in these, a method that quantifies resting time of the entire muscles is needed. Such a method, 'muscular rest', was further developed and validated. It discriminated well between workers in occupations with high and low prevalence of neck/shoulder myalgia. EMG is, moreover, extensively used to assess the level of muscular activity during work. Large differences have been shown between individuals that perform the same work task, which could be due to differences in strength or working technique, or to a measurement error. The precision of the method has been poorly known. Six females repeated three different work tasks at three different occasions. For m.trapezius, the variation between days (within individual) was small, 8%. For the forearm extensors, it was somewhat larger, 33%, probably because of less adequate normalisation. To study the impact of gender on the development of neck and upper limb disorders, 105 males and 172 females with identical repetitive and force demanding work tasks were examined. The prevalence of disorders was much higher among the females. Further, the physical exposure was quantified, separately for the genders, by EMG, as well as by inclinometry and goniometry for working postures and movements. When normalising to a maximal exertion, a significant difference was shown, with higher exposures for females. The relative peak load was 50% higher for m.trapezius, and 44% higher for the forearm extensors. Further, females had 45% less muscular rest in the forearm extensors, and 40% higher wrist flexion/extension velocity on the right side. It is likely that a substantial share of the excess morbidity among females can be explained by higher physical exposure at work

Finger Flexor Tendon Orientation and Location as a Function of Postural Changes of the Wrist and Forearm: The Quantification of Musculoskeletal Loading in Jobs with Deviated Forearms

Forearm pronation/supination is common during manual activities, and has been linked to upper limb disorders in the workplace (Hughes et al. 1997). Forearm deviations from neutral (palm of the hand facing medially) can increase discomfort and forearm musculature activity (EMG) (Khan 2009a; Domizio & Keir, 2010), particularly when combined with wrist postures deviated from neutral. Yet ergonomic tools commonly used to assess the risk of developing distal upper limb disorders (e.g., Strain Index and RULA), often disregard or only minimally account for forearm pronation/supination posture. As a result, the risk of injury may be underestimated. This dissertation first examined methods of measuring pronation in the workplace by testing instantaneous agreement of forearm posture measurements between Inertial Motion Units (Xsens, Netherlands) and a laboratory-based motion capture system (Vicon, UK). Participants turned metallic and non-metallic handles in front of them, in order to quantify the effect of magnetic disturbance and sensor orientation on the Xsens. On average, RMSE errors of 12.6 deg around metal, and 8.6 deg around plastic were observed on instantaneous measures. Higher rotational velocities appeared associated with larger errors. Summarized data revealed smaller discrepancies. Second, this dissertation examined the effect of forearm pronation/supination coupled with wrist flexion/extension on the orientation and location of finger flexor tendons with respect to a radial coordinate system, using MRI of 4 healthy wrists. Pronation/supination caused movement almost exclusively in the frontal plane. Radial tendons exhibited larger angular deviations in pronation, whereas ulnar tendons were nearly straight, and the opposite was observed in supination. Larger angular deviations were thought to increase contact forces within the tunnel in the direction of the bend, which combined with finger movement could increase the risk of tenosynovitis. Finally the results of these studies were combined to measure tendon movement during a repetitive task. The three tendons with the greatest angular movement in the tunnel were: FDP2 (0.16 deg/pronation/supination degree), FDS3 (0.15 deg/ pronation/supination degree), and FDS4 (0.17 deg/ pronation/supination degree)

Topics in construction safety and health : ergonomic hazards and WMSDs : an interdisciplinary annotated bibliography

"These referenced articles provide literature on construction workers and their risk of ergonomic hazards and work-related musculoskeletal system disorders on the job." - NIOSHTIC-2NIOSHTIC no. 20068246Production of this document was supported by cooperative agreement OH 009762 from the National Institute for Occupational Safety and Health (NIOSH). The contents are solely the responsibility of the authors and do not necessarily represent the official views of NIOSH.Ergonomics-and-WMSDs-annotated-bibliography.pdfcooperative agreement OH 009762 from the National Institute for Occupational Safety and Healt

How visual ergonomics interventions influence health and performance - with an emphasis on non-computer work tasks

Visual ergonomics evaluations and interventions were performed on non-computer work tasks at recycling facilities, post sorting facilities and operating theatres. The results can to some extent be applicable to other professions and workplaces. The purpose of the research was to investigate the effects of visual ergonomics interventions on eyestrain, musculoskeletal discomfort, headache, and visual performance at work. Individuals with eyestrain reported more musculoskeletal discomfort than individuals without eyestrain. Factors shown to have an impact on eyestrain and musculoskeletal discomfort were the visual environment, the individual’s perceived visual ability and need for spectacles. Such findings have been reported among computer users. The results presented here show that non-computer work tasks may induce similar findings as well. Evaluations of workplaces and interventions with lighting and spectacles were performed in the studies presented in this thesis. The interventions were evaluated by direct observations such as an expert approach and by indirect observations by means of questionnaires. After the evaluation and measurement of the lighting at the recycling facilities, a number of lighting recommendations were suggested to increase visibility and reduce accident risks. For the younger postal workers in particular, better lighting reduced eyestrain and musculoskeletal discomfort. Pre-intervention, the individuals with eyestrain had lower productivity than those without; their productivity increased with better lighting. The musculoskeletal discomfort from the neck decreased especially from the static side for the postal workers after they were provided with correct power in their spectacles. It is possible to improve the work posture of presbyopic postal workers with customised sorting spectacles, in particular because using the sorting spectacles results in a decrease of the backward tilt of the head. In visually demanding work such as surgery, the luminance contrast within the visual field is essential. This is especially the case for the scrub nurse who has to look into the very bright operating light and also see the less highly lit instrument table and other important aspects in the operating room. The visual focus of the surgeons is in the operating cavity, and their eyes are completely adjusted to that level. It can take up to two minutes before their vision is fully functioning again after being exposed to the high illuminance from the operating cavity. This poses a risk if something happens in the operating room outside the operating cavity that requires good visibility from the surgeon. It is thus vital to increase the general lighting in an operating room, especially around the operating table, to decrease the luminance contrasts and facilitate the operating personnel’s visual ability. In this intervention study, the operating personnel rated the improved lighting as improving their perceived visual ability and a decreasing tiredness. All together, the studies show that visual ergonomics is a multidisciplinary science that requires a holistic approach. This thesis will hopefully contribute to increasing the awareness of the effects of a good visual environment and its benefits for the individual’s health

Worker and Public Health and Safety

This book on "Worker and Public Health and Safety: Current Views" brings together current scholarly work and opinions in the form of original papers and reviews related to this field of study. It provides important and recent scientific reading as well as topical medical and occupational information and research in areas of immediate relevance, such as chronic and occupational diseases, worker safety and performance, job strain, workload, injuries, accident and errors, risks and management, fitness, burnout, psychological and mental disorders including stress, therapy, job satisfaction, musculoskeletal symptoms and pain, socio-economic factors, dust pollution, pesticides, noise, pathogens, and related areas

Fatigue at the Workplace: Measurement and Temporal Development

Fatigue at the workplace has been described as a multidimensional construct, affecting the overall state of the whole organism, which may be a consequence of prolonged work and various psychological, socioeconomic, and environmental factors. In the short term, fatigue may lead to discomfort, diminished motor control, reduced proprioception, increased force variability, and reduced strength capability, resulting in reduced performance, lowered productivity, deficits in work quality, and increased incidence of accidents and human errors. Fatigue may also lead to longer-term adverse health outcomes such as chronic fatigue syndrome, myalgia, and burnout syndromes, and may be a precursor to WMSDs – work-related musculoskeletal disorders. If indeed fatigue is a precursor to WMSDs and other long-term health outcomes, it may then be a relevant biomarker for cumulative exposure to repetitive and/or sustained work, and thus a useful risk indicator and/or a design and evaluation tool. However, little is known of the temporal pattern of fatigue development and its relationships with disorder risks and work performance. The objective of this thesis was to identify and evaluate a battery of fatigue measures for both laboratory and field-based research, and provide insight into fatigue development in work-relevant task conditions. Six studies were designed to address these objectives. In the first study, measures and analysis methods that detect fatigue-related changes were identified by a group of expert fatigue researchers. The second was an exploratory study focused on the responsiveness of a select number of measures during a workday and multiple workdays in realistic physically demanding residential plumbing work. In the third study, a selected number of conventional and novel measures were evaluated for their reliability and sensitivity in a controlled laboratory setting. This study also addressed the responsiveness of measures during a test battery or during the fatiguing activity (i.e., continuously), and the time between cessation of activity and test battery in which measures remain responsive. The fourth study reported on whether circadian effects were detectable by selected measures, providing insight towards the daylong reliability of these measures. In the fifth study, measures were evaluated in four fatiguing conditions, representing changes in type of contraction, intensity, and body segment. Furthermore, the pattern of fatigue development and the temporal responsiveness of measures were described. Finally, measures were assessed over an 8-hour light precision micropipetting task to investigate temporal responsiveness of measures and fatigue development. Errors were quantified and the effects of scheduled work breaks were reported. In study 1, fifty-seven measures were identified based on outcomes and/or effects of fatigue in the workplace. Based on the perceived validity, reliability, and practicality in laboratory and field investigations, four measures were recommended for both settings: maximum voluntary contractions, questionnaires and fatigue scales, Borg’s rating of perceived exercise or discomfort, and visual analog scales. On the other hand, twenty-five measures were not recommended for field studies, including methods traditionally recognized as “gold standard” in measuring cellular and metabolic changes. In study 2, fatigue was documented in realistic physically demanding work while employing a set of measures to provide a comprehensive picture of fatigue development. Not all measures revealed increasing fatigue over the workday or over the workweek, which may be a result of measures reflecting different fatigue processes. Thus, the study reinforced the need of a complementary set of measures, reflecting multiple domains, to measure and interpret the temporal development of fatigue. Two measures, rating of perceived discomfort and grip strength, indicated significant differences within a work day, notably an increase at the beginning and end of the shift (perceived discomfort) and a decrease between mid-shift and end of shift (grip strength). It was speculated that within-day trends were consistent with central fatigue mechanisms. Over multiple workdays, both central and peripheral components displayed a significant day effect. Fatigue accumulation over the workweek was observed with grip strength, physiological resting tremor, and postural tremor measures, particularly between day 1 (Tuesday) and day 4 (Friday). In study 3, test-retest reliability ranged between “poor agreement” and “almost perfect agreement”. In terms of sensitivity, action tremor, MMG RMS amplitude, postural tremor, and rating of perceived fatigue were highly responsive. Perceived fatigue remained elevated, relative to baseline, until 11 minutes post-exercise. Postural and physiological tremor persisted from baseline until the third minute of recovery. Action tremor, however, quickly recovered within the first minute of recovery. This current study found that for most of the measures, there were no statistical differences between test battery and continuous measurement, but a few measures were approaching statistical significance. Action tremor and mechanomyography collected during a test contraction, and perceived fatigue assessed by a visual analog scale, were found to be most reliable, most responsive, comparable to continuous measures, and sensitive after the fatiguing activity, and should be considered with other measures of interest, as part of a test battery. In study 4, only two measures revealed a statistically significant time-of-day effect: mechanomyography of a flexor forearm muscle and action tremor at 30% MVC. These two measures exhibited rhythmicity based on cosinor analysis. Therefore a degree of caution might be required when interpreting daylong fatigue with these two measures, whereas the other measures may not be susceptible to, or detect, significant diurnal effects. Although the remaining measures did not reveal statistically significant time effects, most measures were characterized with similar patterns to those found in previous literature. In study 5, there was no one universal measure that was common, in terms of responsiveness, in all exercise conditions. Although no single measure was found to be most responsive in all conditions, there were measures responsive in most exercise conditions as either a continuous or test battery measure. This was the case with action tremor. A maximum voluntary contraction, which is dependent on processes in both central and peripheral domains, was similarly responsive. Rating of perceived fatigue, which has been cited as a centrally mediated indicator, was also found to increase with exercise progression in hand conditions. Therefore fatigue measures, reflecting changes to both central and peripheral processes, may be useful in measuring tasks and exercises of varying parameters. In this study, we support earlier investigations on the pattern of fatigue development in isometric and time-varying (e.g., intermittent isometric, concentric) contractions. The temporal responsiveness of central and peripheral measures, on the other hand, may be a better reflection of the intensity of the task. The shoulder intermittent condition was not consistent with the expected pattern for an intermittent isometric contraction. However, the study protocol may have inadvertently generated lower muscle activity, and therefore the extent of fatigue may have been minimal. There remains a need to understand complex combinations of task-dependent factors in both fatigue development and temporal responsiveness. In study 6, nine measurement parameters revealed significant increases in fatigue over the work period. Traditional field measures (i.e., MVC and EMG) did not lead to extraordinary time effects. Error rates followed similar trends to the 9 significant measurements: an increase from baseline towards mid-morning, a slight decrease prior to the lunch break, a nadir after lunch, and increasing fatigue effects over the course of the afternoon. Error rates, however, might not be a sole consequence of fatigue – cognitive and physical; but might also reflect changes in arousal level. Over the pipetting task, there was interplay between peripheral and central fatigue mechanisms in three body segments: thumb, hand, and shoulder. Fatigue developed at a “local” level (i.e., at the three body segments) and was consistent with expected patterns observed in study 5, particularly if thumb and shoulder actions were considered concentric actions and the grip force was a sustained isometric contraction. Overall, the collective assessments suggested that rating of perceived fatigue and action tremor, on average, were highly repeatable and responsive in multiple task conditions. Postural tremor or steadiness and maximum voluntary contractions were moderately reliable and responsive. Different forms of tremor may be responsive to different task conditions. Postural tremor amplitude was found to increase over the course of an 8-hour workday in a light precision work task, and over multiple days in physically demanding work. Action tremor, on the other hand, appeared to be responsive at higher work intensities performed at a shorter duration of time. Possibly, action tremor may be more indicative of changes in the periphery, whereas postural tremor reflects changes more central in nature. Consequently, these measures should be considered for inclusion into a test battery for field use. For the ergonomist or health and safety practitioner, this body of work provides some insight into the utility of a test battery of fatigue measures to complement current task analysis techniques. For workplace researchers, this dissertation provides insight into the temporal development of fatigue in various task conditions and the reliability and responsiveness of select measures in both short and longer-term work-studies. This research might subsequently elicit future investigations in the relationship between work exposure, fatigue development, and performance and longer-term health outcomes

Body sensor networks: smart monitoring solutions after reconstructive surgery

Advances in reconstructive surgery are providing treatment options in the face of major trauma and cancer. Body Sensor Networks (BSN) have the potential to offer smart solutions to a range of clinical challenges. The aim of this thesis was to review the current state of the art devices, then develop and apply bespoke technologies developed by the Hamlyn Centre BSN engineering team supported by the EPSRC ESPRIT programme to deliver post-operative monitoring options for patients undergoing reconstructive surgery. A wireless optical sensor was developed to provide a continuous monitoring solution for free tissue transplants (free flaps). By recording backscattered light from 2 different source wavelengths, we were able to estimate the oxygenation of the superficial microvasculature. In a custom-made upper limb pressure cuff model, forearm deoxygenation measured by our sensor and gold standard equipment showed strong correlations, with incremental reductions in response to increased cuff inflation durations. Such a device might allow early detection of flap failure, optimising the likelihood of flap salvage. An ear-worn activity recognition sensor was utilised to provide a platform capable of facilitating objective assessment of functional mobility. This work evolved from an initial feasibility study in a knee replacement cohort, to a larger clinical trial designed to establish a novel mobility score in patients recovering from open tibial fractures (OTF). The Hamlyn Mobility Score (HMS) assesses mobility over 3 activities of daily living: walking, stair climbing, and standing from a chair. Sensor-derived parameters including variation in both temporal and force aspects of gait were validated to measure differences in performance in line with fracture severity, which also matched questionnaire-based assessments. Monitoring the OTF cohort over 12 months with the HMS allowed functional recovery to be profiled in great detail. Further, a novel finding of continued improvements in walking quality after a plateau in walking quantity was demonstrated objectively. The methods described in this thesis provide an opportunity to revamp the recovery paradigm through continuous, objective patient monitoring along with self-directed, personalised rehabilitation strategies, which has the potential to improve both the quality and cost-effectiveness of reconstructive surgery services.Open Acces

Sports Performance and Health

Sports performance is primarily associated with elite sport, however, recreational athletes are increasingly attempting to emulate elite athletes. Performance optimization is distinctly multidisciplinary. Optimized training concepts and the use of state-of-the-art technologies are crucial for improving performance. However, sports performance enhancement is in constant conflict with the protection of athletes’ health. Notwithstanding the known positive effects of physical activity on health, the prevention and management of sports injuries remain major challenges to be addressed. Accordingly, this Special Issue on "Sports Performance and Health" consists of 17 original research papers, one review paper, and one commentary, and covers a wide range of topics related to fatigue, movement asymmetries, optimization of sports performance by training, technique, and/or tactics enhancements, prevention and management of sports injuries, optimization of sports equipment to increase performance and/or decrease the risk of injury, and innovations for sports performance, health, and load monitoring. As this Special Issue offers several new insights and multidisciplinary perspectives on sports performance and health, readers from around the world who work in these areas are expected to benefit from this Special Issue collection