The effects of lumbar massage on muscle fatigue,muscle oxygenation,low back discomfort,and driver performance during prolonged driving

This paper reviews results of comparisons between novice and expert operators in the supervision of dynamic environments. Firstly, the characteristics of expertise and its operational definitions are discussed. Secondly, the main dimensions of the complexity of these environments are described and the difficulties operators have in coping with complexity are examined. Research work carried out in field studies is then overviewed in order to assess the role of expertise in the three components of process control: monitoring, diagnosis and decision-making and executive control. The discussion stresses the convergent results of various studies. In spite of the diversity of task domains and of novice-expert definitions, results converge on three points: experts are better at producing inference, in anticipating, and have a more functional view of the process. Divergent results on directionality of reasoning, depth of knowledge in relation to performance and synchronization of actions are also discussed. Finally, further research trends are outlined.     

Evaluation of document location during computer use in terms of neck muscle activity and neck movement

This study evaluated the impact on neck movement and muscle activity of placing documents in three commonly used locations: in-line, flat desktop left of the keyboard and laterally placed level with the computer screen. Neck excursion during three standard head movements between the computer monitor and each document location and neck extensor and upper trapezius muscle activity during a 5 min typing task for each of the document locations was measured in 20 healthy participants. Results indicated that muscle activity and neck flexion were least when documents were placed laterally suggesting it may be the optimal location. The desktop option produced both the greatest neck movement and muscle activity in all muscle groups. The in-line document location required significantly more neck flexion but less lateral flexion and rotation than the laterally placed document. Evaluation of other holders is needed to guide decision making for this commonly used office equipment.     

The influence of desk and display design on posture and muscle activity variability whilst performing information technology tasks

Desk design and computer display height can affect posture and muscle activation during computer use. Amplitudes of postural variables and muscle activity during computer use do not explain the results from epidemiological studies of musculoskeletal discomfort and disorders related to computer use. The purpose of this study was to assess variability of posture and muscle activity during work with two computer display heights and book/paper, in conjunction with a curved desk designed to provide forearm support and a traditional, straight desk.18 male and 18 female participants performed 10-min tasks involving keying, mousing, reading and writing in six desk/display conditions. 3D posture and surface emg were assessed for the final 2 min of each task.The curved desk resulted in greater postural and muscle activity variation, suggesting an advantage of this supportive surface over the straight desk. There was little difference in variability associated with the two display heights. However, greater variability of posture and muscle activity was evident with the book/paper condition. Non-touch typists had greater neck flexion variation.The design of information technology tasks and workstations can influence the short term variation in posture and muscle activity. Variation is influenced independently of mean postures and muscle amplitudes and therefore needs to be considered to adequately assess the risk of musculoskeletal disorders.     

Effect of load mass on posture, heart rate and subjective responses of recreational female hikers to prolonged load carriage

Load carriage has been associated with a risk of upper and lower limb musculoskeletal disorders with women suffering significantly higher injury rates than their male counterparts. Despite this injury risk, there are limited evidence-based guidelines for recreational hikers, particularly female recreational hikers, regarding safe backpack loads. The purpose of the present study was to determine how variations in load mass affected the heart rate, posture and subjective responses of women during prolonged walking to provide evidence for a load mass limit for female recreational hikers. Heart rate (HR), posture and ratings of perceived exertion (RPE) and discomfort were collected for 15 female experienced recreational hikers (22.3 ± 3.9 years) while they hiked for 8 km at a self-selected pace under four different load conditions (0%, 20%, 30% and 40% of body weight (BW)). Although HR was not significantly affected by load mass or walking distance, increasing load mass and distance significantly affected posture, RPE and discomfort of the upper body. Carrying a 20% BW load induced significant changes in trunk posture, RPE and reported shoulder discomfort compared to the unloaded condition. The 20% BW load also resulted in a mean RPE rating of ‘fairly light’, which increased to ‘hard’ when carrying a 40% BW load. As load carriage distance increased participants reported significantly increased shoulder, neck and upper back discomfort. Based on the changes to posture, self-reported exertion and discomfort when carrying loads of 20%, 30% and 40% BW over 8 km, it was concluded that a backpack load limit of 30% BW should be recommended for female recreational hikers during prolonged walking.     

Evaluation of upper-limb body postures based on the effects of back and shoulder flexion angles on subjective discomfort ratings,heart rates and muscle activities

A possible limitation of many ergonomics checklists that evaluate postures is an independent evaluation of each body segment without considering the coordination between body segments and resulting in the under-/over-estimation of body postures. A total of 20 men were selected to evaluate the effects of shoulder and back flexion angles on the upper-limb muscle activities, subjective discomforts and heart rates. Interesting findings were obtained from the coordination between back flexion angles and shoulder flexion angles. At a back flexion angle of 45°, the discomfort and heart rates were the least at a shoulder flexion angle of 45°. The %MVC also showed a similar trend. It could be inferred that the 0° shoulder flexion angle would be a natural posture, when the back flexion angle is 0°, whereas 45° shoulder flexion might be a more natural posture when the back flexion angle is 45°.

Statement of Relevance: This study evaluated the effects of back and shoulder flexion angles on subjective as well as objective measures. The findings of this study considered the coordination between two body flexion angles and could be used to improve the accuracy of existing ergonomics evaluation methods for body postures.     

Serial analyses of postmortem changes in human skeletal muscle: A case study of alterations in proteome profile, histology, electrolyte contents, water composition, and enzyme activity

Postmortem tissues are frequently used in forensic investigation, clinical studies, and biomedical research. It is well known that the shorter period from death to analyses provides the more accurate results. However, the longest postmortem interval that still provides the reliable data remains unclear. We performed serial analyses of postmortem changes in proteome profile, histology, electrolyte contents, water composition, and enzyme activity in human vastus lateralis muscle from a male cadaver (died from a motorcycle accident). This uninjured muscle was sectioned into several 1‐cm³ cubes and stored in individual closed tubes at 4 or 25°C for 0, 2, 4, 6, 12, 24 or 48 h prior to proteomic, histological, chemical and biochemical analyses. At 4°C, the 2‐DE proteome profile remained unchanged until 24 h, when some poorly focused protein spots and significant decrease in the total number of visualized spots were observed. These changes were detectable earlier (12 h) in the samples stored at 25°C. Profound vacuolization and autolysis started at 24 and 6 h for the samples stored at 4ºC and 25°C, respectively. K and Mg contents began to increase at 12 and 48 h, respectively, for both temperatures. However, the increase in Na and Ca contents began at 24 h in the samples stored at 4°C, but started earlier (12 h) in those stored at 25°C. Water content started to decline at 48 and 24 h in the samples stored at 4 and 25°C, respectively. Muscle lactate dehydrogenase activity began to be out of range at 12 h for both temperatures. These findings demonstrate that storing the samples at 4°C could delay some of the aforementioned changes, which occurred more rapidly at 25°C. Our results also suggest that muscle proteome profile, histology, electrolyte contents, water composition, and enzyme activity should be analyzed within the optimal postmortem intervals, which vary among individual analyses, to obtain the most reliable data.     

The analysis of heart rate variability in unrestrained rats. Validation of method and results

An experimental setting and software were developed to evaluate cardiac autonomic function in unrestrained rats. Subcutaneously implanted ECG electrodes and an indwelling venous catheter were tunneled to a tail cuff in five rats. The ECG was A/D converted at 1000 Hz. After peak detection, a time series of RR intervals was obtained. Programs for the analysis of heart rate variability (HRV) were implemented in LabVIEW. Statistical properties were determined in the time domain. After cubic spline function curve fitting, resampling at 0.1 s and test for stationarity, power spectral analysis was performed on sampled records of 30 min duration after applying a sliding Hanning window (Welch method: 256 points (duration 25.6 s), 50% overlap and 0.039 Hz resolution). Algorithms were tested with simulated signals consisting of isolated frequency components, which were retrieved at their exact locations. Physiological validation of the system was performed by, β-adrenergic and cholinergic blockade and by forced breathing at a fixed rate. Measurements were performed on five unrestrained rats under basal conditions. Mean RR was 174.2±3.6 ms; S.D., 13.3±4.6 ms; rMSSD, 5.2±1.2 ms; pNN10, 3.5±1.9% and pNN5, 18.7±6.4%. Low (0.19–0.74 Hz) and high frequency (0.78–2.5 Hz) power were determined (and also percent of low to total and high to total): 18.42±10.74 ms² (22.9±6.5%) and 15.66±5.56 ms² (19.9±2.7%), and the ratio low/high: 1.16±0.39. In conclusion, HRV analysis programs were developed and thoroughly tested through simulations and in vivo, under basal conditions and after pharmacological blockades. Using this software, HRV data from unrestrained rats were obtained.     

The moderating role of end-tidal CO2 on upper trapezius muscle activity in response to sustained attention

With higher levels of automation in modern manufacturing, there is increased monitoring of the process by the human operator. Prolonged monitoring or sustained attention has been found to be stressful for human operators. Plant and process operators have also been found to have one of the highest level of work demands (work speed, pace) in a recent European survey (Eurofound, 2015). Along with this, the incidence of Work Related Musculoskeletal Disorders (WRMSDs) remains at a high level in the manufacturing sector. This research endeavoured to determine if end-tidal CO₂ levels decreased and upper trapezius muscle activity increased concurrently with increased levels of attention. We then developed a model to investigate if end-tidal CO₂ moderated the relationship between mental workload due to sustained attention and upper trapezius muscle activity. The resulting interactional model found that end-tidal CO₂ moderated the relationship (p = 0.004) when end-tidal CO₂ reached the hypocapnic range (>35 mm Hg). This model indicates the possibility that a high level of sustained attention is a risk factor in the development of WRMSDs and should therefore be included in workplace risk assessments.     

Effects of dynamic,static and combined work on heart rate and oxygen consumption

The effects upon heart rate and oxygen consumption of muscular exercises including simultaneous dynamic and static contractions were studied in three male subjects. Dynamic work consisted of walking at four speeds (0·56, 0·83, 1·11, 1·39 m s^?) on a horizontal treadmill; static work consisted of pushing against, pulling and holding 6, 9, 12, 18 and 24?kg; combined work associated walking with each one of the forms of static work. Physiological load is expressed in terms of cardiac cost (ΔHR) and oxygen cost (Δ[Vdot]_o2). The physiological cost of combined work increases with both the walking speed and the static load. For each parameter (HR and [Vdot]_o2) the extra-cost of combined work has been determined by computing the difference between the cost of combined work and the sum of the costs observed during static and dynamic exercises separately performed. The paired t-test shows significant differences for all of the walking-pushing tests, but only for 8 pulling tests and 2 holding tests. Linear relationships are observed between the oxygen extra-cost and load when walking at 0·56 or 0·83 ms^?1, with correlation coefficients statistically significant for pushing and pulling (p < 0·01) but not significant for holding tests. The present results show that, when the static work is combined with walking, the physiological response varies with the type of static work considered.     

Influence of wearing an unstable shoe on thigh and leg muscle activity and venous response in upright standing

Purpose

To quantify the effect of unstable shoe wearing on muscle activity and haemodynamic response during standing.

Methods

Thirty volunteers were divided into 2 groups: the experimental group wore an unstable shoe for 8 weeks, while the control group used a conventional shoe for the same period. Muscle activity of the medial gastrocnemius, tibialis anterior, rectus femoris and biceps femoris and venous circulation were assessed in quiet standing with the unstable shoe and barefoot.

Results

In the first measurement there was an increase in medial gastrocnemius activity in all volunteers while wearing the unstable shoe. On the other hand, after wearing the unstable shoe for eight weeks these differences were not verified. Venous return increased in subjects wearing the unstable shoe before and after training.

Conclusions

The unstable shoe produced changes in electromyographic characteristics which were advantageous for venous circulation even after training accommodation by the neuromuscular system.     

Effects of changes in sitting work posture on static neck and shoulder muscle activity

Abstract

In order to analyse the effect of changing the sitting posture on the level of neck and shoulder muscular activity, an electromyographic (EMG) study of ten healthy experienced female workers from an electronics plant was undertaken. A standardized, simulated task was performed in eight different sitting work postures. Using surface electrodes, the level of muscular activity was recorded as normalized, full-wave rectified low-pass filtered EMG. The results showed that the whole spine flexed sitting posture gave higher levels of static activity in several neck and shoulder muscles than the posture with a straight and vertical spine, which in turn gave higher levels than the posture with slightly backward-inclined thoraco-lumbar spine.     

Design,realization and user evaluation of the SmartVortex Visual Query System for accessing data streams in industrial engineering applications

Objective: In this paper we present a Visual Query System, which allows users to graphically build queries over data streams and traditional relational data. The Visual Query System runs on top of a DSMS (Data Stream Management System).Methods: The system has been designed and implemented following the user-centered design approach. Two different releases of the system have been incrementally and iteratively designed and evaluated. The first release has been evaluated using heuristic evaluation. The second release, whose design was a refinement based on the results of the foregoing heuristic evaluation, was evaluated by several users. Moreover, a comparative evaluation involving users has been conducted on the second release.Results: The paper presents the visual query system, and the results ofthe various evaluations.Conclusion: Visual Query Systems for data streams are an effective tool for industrial engineers in querying and analyzing data streams from equipments.Practice and implications: The proposed visual query system has been employed in real industrial scenarios in order to visually query and analyze data streams produced by industrial machines.     

Effect of a desk attachment board on posture and muscle activity in women during computer work

Working at a computer is part of a large number of jobs and has been associated with upper extremity musculoskeletal disorders and back pain. The study evaluated the effects of a board attachment on upper extremity and back. The findings are mixed in that the board may have a positive effect in preventing back pain, but may be detrimental to upper extremities. Effect of a desk attachment board on upper extremity and trunk posture, and muscle activity was assessed in women video display terminal users. Participants completed a standard 20-min computer task under two conditions: 1) using a standard desk; 2) using a desk attachment board designed to support the forearms. Bilateral electromyography of the trapezius, multifidus and longissimus muscles and the right anterior deltoid and forearm extensor muscles was recorded. 3-D trunk and upper extremity posture was monitored. Participants were tested before and after 2 weeks of familiarisation with the board in their workplace. Perceived tension and discomfort were recorded before and after use of the board. Use of the board tended to increase muscle activity in the right trapezius and forearm extensor and to decrease muscle activity in the back. Perceived tension in the low back decreased slightly with the board. The board may be useful in reducing tension in the low back during computer work, but may adversely affect the upper extremities.     

基于虚拟样车、逆求工程及异地并行设计技术的汽车车架设计、开发系统研究

文章在分析汽车制造行业设计、开发过程特点的基础上,指出在汽车制造行业设计、开发过程中引入并行工程的必要性,并提出了一种基于虚拟样车、逆求工程及产品异地并行设计技术的并行工程开发系统,详细叙述了其系统结构及技术支撑。     

Effects of bath chairs on the behavior,muscle workload,and experience in independent bathing of the elderly: A Chinese case study

It is important to use a bath chair for reducing the injury risk in elderly independent bathing and for improving the elderly bathing experience. This study aimed to investigate the elderly independent bathing process and the effect of bath chairs on the elderly. We investigated the bath scenarios of elderly Chinese people through a questionnaire and behavior observation. Then, based on the survey results, we designed an experiment to evaluate the muscle workload and subjective experience in twelve bathing tasks. Twelve elderly participants were recruited to complete the bathing task in two scenarios: with a chair and without a chair. We found Showering was the dominant bathing style for elderly Chinese people. The rectus-femoris and the lumbar-erector workload change differed significantly between the two scenarios when cleaning the lower body, and the subjective experience with a chair was significantly better than that without a chair. The amplitude of the basic motions of the static-work joints significantly affects the workload of corresponding muscles and the bathing experience. The bath chair effectively reduced the workload of the rectus femoris and the lumbar-erector, reducing the risk of falls and improving the subjective experience of the elderly when cleaning the lower body. However, the bath chair had limited improvement in the workload of the rectus femoris and the lumbar-erector during some bathing tasks, which was the main direction of the bath-chair optimization. This study helps to evaluate the elderly bathing experience, and optimizes bath-chair design.     

Effects of restrictive clothing on lumbar range of motion and trunk muscle activity in young adult worker manual material handling

The objective of this study was to examine the effect of wearing restrictive trousers on lumbar spine movement, trunk muscle activity and low back discomfort (LBD) in simulations of manual material handling (MMH) tasks. Twenty-eight young adults participated in the study performing box lifting, liquid container handling while squatting, and forward reaching while sitting on a task chair when wearing tight pants (sizes too small for the wearer) vs. fit pants (correct size according to anthropometry). Each task was repeated three times and video recordings were used as a basis for measuring lumbar range of motion (LRoM). The response was normalized in terms on baseline hip mobility. Trunk muscle activity of rectus abdominis (RA) and erector spinae (ES) muscles were also measured in each trial and normalized. At the close of each trial, participants rated LBD using a visual analog scale. Results revealed significant effects of both pants and task types on the normalized LRoM, trunk muscle activity and subjective ratings of LBD. The LRoM was higher and trunk muscle (ES) activity was lower for participants when wearing tight pants, as compared to fit pants. Discomfort ratings were significantly higher for tight pants than fit. These results provide guidance for recommendations on work clothing fit in specific types of MMH activities in order to reduce the potential of low-back pain among younger workers in industrial companies.     

Evaluation of five steering input devices in terms of muscle activity,upper body kinematics and steering performance during heavy machine simulator driving

Work related upper body musculoskeletal symptoms and disorders constitute a major problem for operators of heavy machinery. Steering input devices mediate risk factors of upper body musculoskeletal disorders. Little research has been conducted to compare the multiple commercially available steering input devices in a multi-faceted approach. The present study evaluated five commonly used steering input devices (conventional steering wheel, fast steering wheel, miniature steering wheel, first-order joystick and second-order joystick) in terms of muscle activity, upper body kinematics and steering performance during heavy machine simulator driving. Fifteen healthy males novice to operation of heavy machinery completed five laps on a simulated track with each steering input device. Results showed a generally lower muscle activity when using the joysticks. The conventional and fast steering wheel increased mean wrist and shoulder flexion/extension angles and participants spent more time in wrist flexion/extension angles corresponding to moderate and poor comfort levels. An increased elbow protonation angle was found for the three steering wheels compared to the joysticks. The conventional steering wheel showed slowest track completion time and was subjectively ranked worst. The first-order joystick was ranked highest but also showed the highest amount of steering reversal rates, posing a risk of increased repetitiveness. Overall, the second-order joystick is considered superior ergonomically compared to the other steering input devices evaluated. However, all evaluated steering input devices exceeded muscle activity and/or joint angle recommendations.Relevance to the industry: Compared to steering wheels, joystick steering showed reduced muscular activity and less awkward joint postures, suggesting a reduced risk of developing musculoskeletal disorders in the long term. However, the results warrant efforts to further develop joystick steering resulting in a reduction of exposure level beyond the existing solutions.     

The effects of knee angles on subjective discomfort ratings, heart rates, and muscle fatigue of lower extremities in static-sustaining tasks

The purpose of this study was to investigate the effects of knee-flexion angles on subjective discomfort ratings, heart rates, and muscle fatigue using median frequency (MDF) in a static-sustaining task. Thirty healthy participants maintained 13 postures including standing, squatting, sitting, and kneeling postures and then MDFs from the erector spinae, biceps femoris, vastus medialis, gastrocnemius, and tibialis anterior muscles, subjective discomfort, and heart rates were collected every 3 min during a sustained 15 min task. Results showed that the discomfort, heart rate and muscle fatigue were significantly influenced by the body postures. In general, standing and sitting postures showed less discomfort as well as lower heart rates, whereas squatting postures (KF120, KF90, KF60) had higher discomfort and heart rates. Three MDF change trends were reported associated with postures in this study. First, there were less changes of MDFs for standing and sitting postures; second, all patterns of MDFs for KF 150 and KF120 decreased, and lastly some MDFs had increasing trends and others showed decreasing trends for KF30, KF30T, and kneeling postures.     

Ergonomic evaluation of the musculoskeletal risks in a banana harvesting activity through qualitative and quantitative measures,with emphasis on motion capture (Xsens) and EMG

The objective of this study was to evaluate the risk of musculoskeletal injuries in a banana processing task. A sample of three workers were evaluated with the Nordic questionnaire as well as according to effort, discomfort and usability levels, hand grip dynamometry, inertial sensor motion capture (Xsens) and surface electromyography in the right arm. The workers had musculoskeletal complaints throughout the spine and hips, low effort and discomfort levels, and a satisfactory usability level. The hand grip strength values (dominant: 54.8 Kgf; non-dominant: 54.2 Kgf) were above the reference values for the Brazilian population. Regarding movement analysis, we identified risks related to cervical protrusion, forward and lateral trunk flexion, abduction and flexion in the shoulders, flexion, extension, radial and ulnar deviation in the wrists, as well as repetitive movements. Surface electromyography showed that the greatest demand during the task was on the extensor carpi radialis, although the trapezius and flexor carpi radialis showed a tendency toward fatigue. Thus, the set of evaluations showed that the tool used and worker adaptation to the position of the bunches, together with the repetitious movement, led to inadequate postures and musculoskeletal risks.Relevance to industryThe banana processing activity generates employment and income in several regions of the world and in Brazil. However, it is still rudimentary and may present risks to the worker's health. This study seeks to elucidate ergonomic risks through technological instrumentation in order to have a quantitative assessment of the ergonomic risks.