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Textbook Of Work Physiology Physiological Bases Of Exercise

Research in closed-loop supply chains (CLSCs) has grown rapidly over the last 10 years. The authors offer a critical review of influential CLSC research that takes a business economics perspective. Much of the research was inspired by practice-driven thoughtpieces, and this helped to keep research focused on relevant issues. However, CLSC research has several assumptions, such as perfect substitution between new and remanufactured products that risk becoming institutionalized. There is a strong need to carefully examine current industrial practice so that research remains focused on relevant problems. Deeper understanding of consumer perceptions of remanufactured products, product diffusion, and valuation of returned products are needed for the field to continue to add insights into developing sustainable economies.

Production and Operations Management

Work related neck and upper limb symptoms have a multi-factorial origin Possible risk factors are of a physical, psychosocial or personal origin These factors can reinforce each other and their influence can also be mediated by cultural or societal factors Initially, most research on neck and upper limb symptoms focused on work-related physical exposure Nowadays, psychosocial work characteristics are recognized as important risk factors Various models have been developed to offer frameworks for possible pathways, but their empirical support is still not conclusive In part I of this paper an overview is presented of the results of recent epidemiological studies on work related psychosocial and personal risk factors for neck and upper limb symptoms In addition, the interplay between these factors and the possible intermediate role of an individuals work style in this process is explored In contrast to previous reviews, it is now possible to base the conclusions on the effect of work related psychosocial factors on neck and upper limb symptoms on quite a few longitudinal studies These studies show that high work demands or little control at work are often related to these symptoms However, this relationship is neither very strong nor very specific Perceived stress is studied in not as many studies but more consistently related to neck and upper limb symptoms This also applies to general distress or other pain (co-morbidity) Job dissatisfaction does not contribute to neck and upper limb symptoms Too little research on personal characteristics is available to draw any conclusions It is plausible that behavioural aspects, such as work style, are of importance in the etiology of work related upper limb symptoms However, studies concerning these factors are promising but too scarce to draw conclusions Future studies should address these behavioural aspects In part II, the recent studies on the effectiveness of preventive measures for work related neck and upper limb problems are discussed Few randomised or non randomised controlled trials have been carried out to evaluate the effectiveness of individual or organisational interventions to improve work related psychosocial factors Very few have reported on the preventive effect for work related neck and upper limb symptoms Therefore, there is a great need for additional high quality trials before any conclusions on effectiveness of bio-behavioural interventions for reduction of neck and upper limb problems and return to work after these symptoms can be made From the low back pain intervention research can be learned that interventions should best be targeted to both the worker and the organisation and that interventions will only be successful when all stakeholders are involved

Epidemiology of work related neck and upper limb problems: Psychosocial and personal risk factors (Part I) and effective interventions from a bio behavioural perspective (Part II)

Background
Neck pain is common, disabling and costly Exercise is one treatment approach

Objectives
To assess the effectiveness of exercises to improve pain, disability, function, patient satisfaction, quality of life and global perceived effect in adults with neck pain

Search methods
We searched MEDLINE, MANTIS, ClinicalTrialsgov and three other computerized databases up to between January and May 2014 plus additional sources (reference checking, citation searching, contact with authors)

Selection criteria
We included randomized controlled trials (RCTs) comparing single therapeutic exercise with a control for adults suffering from neck pain with or without cervicogenic headache or radiculopathy

Data collection and analysis
Two review authors independently conducted trial selection, data extraction, 'Risk of bias' assessment and clinical relevance The quality of the evidence was assessed using GRADE Meta-analyses were performed for relative risk and standardized mean differences (SMD) with 95% confidence intervals (CIs) after judging clinical and statistical heterogeneity

Main results
Twenty-seven trials (2485 analyzed /3005 randomized participants) met our inclusion criteria

For acute neck pain only, no evidence was found

For chronic neck pain, moderate quality evidence supports 1) cervico-scapulothoracic and upper extremity strength training to improve pain of a moderate to large amount immediately post treatment [pooled SMD (SMDp) -071 (95% CI: -133 to -010)] and at short-term follow-up; 2) scapulothoracic and upper extremity endurance training for slight beneficial effect on pain at immediate post treatment and short-term follow-up; 3) combined cervical, shoulder and scapulothoracic strengthening and stretching exercises varied from a small to large magnitude of beneficial effect on pain at immediate post treatment [SMDp -033 (95% CI: -055 to -010)] and up to long-term follow-up and a medium magnitude of effect improving function at both immediate post treatment and at short-term follow-up [SMDp -045 (95%CI: -072 to -018)]; 4) cervico-scapulothoracic strengthening/stabilization exercises to improve pain and function at intermediate term [SMDp -1490 (95% CI:-2240 to -739)]; 5) Mindfulness exercises (Qigong) minimally improved function but not global perceived effect at short term Low evidence suggests 1) breathing exercises; 2) general fitness training; 3) stretching alone; and 4) feedback exercises combined with pattern synchronization may not change pain or function at immediate post treatment to short-term follow-up Very low evidence suggests neuromuscular eye-neck co-ordination/proprioceptive exercises may improve pain and function at short-term follow-up

For chronic cervicogenic headache, moderate quality evidence supports static-dynamic cervico-scapulothoracic strengthening/endurance exercises including pressure biofeedback immediate post treatment and probably improves pain, function and global perceived effect at long-term follow-up Low grade evidence supports sustained natural apophyseal glides (SNAG) exercises

For acute radiculopathy, low quality evidence suggests a small benefit for pain reduction at immediate post treatment with cervical stretch/strengthening/stabilization exercises

Authors' conclusions
No high quality evidence was found, indicating that there is still uncertainty about the effectiveness of exercise for neck pain Using specific strengthening exercises as a part of routine practice for chronic neck pain, cervicogenic headache and radiculopathy may be beneficial Research showed the use of strengthening and endurance exercises for the cervico-scapulothoracic and shoulder may be beneficial in reducing pain and improving function However, when only stretching exercises were used no beneficial effects may be expected Future research should explore optimal dosage

Exercises for mechanical neck disorders

Learning curve models and applications: Literature review and research directions

Pathophysiology of upper extremity muscle disorders

The objective of the present study was to gain insight into the effects of precision demands and mental pressure on the load of the upper extremity. Two computer mouse tasks were used: an aiming and a tracking task. Upper extremity loading was operationalized as the myo-electric activity of the wrist flexor and extensor and of the trapezius descendens muscles and the applied grip- and click-forces on the computer mouse. Performance measures, reflecting the accuracy in both tasks and the clicking rate in the aiming task, indicated that the levels of the independent variables resulted in distinguishable levels of accuracy and work pace. Precision demands had a small effect on upper extremity loading with a significant increase in the EMG-amplitudes (21%) of the wrist flexors during the aiming tasks. Precision had large effects on performance. Mental pressure had substantial effects on EMG-amplitudes with an increase of 22% in the trapezius when tracking and increases of 41% in the trapezius and 45% and 140% in the wrist extensors and flexors, respectively, when aiming. During aiming, grip- and click-forces increased by 51% and 40% respectively. Mental pressure had small effects on accuracy but large effects on tempo during aiming. Precision demands and mental pressure in aiming and tracking tasks with a computer mouse were found to coincide with increased muscle activity in some upper extremity muscles and increased force exertion on the computer mouse. Mental pressure caused significant effects on these parameters more often than precision demands. Precision and mental pressure were found to have effects on performance, with precision effects being significant for all performance measures studied and mental pressure effects for some of them. The results of this study suggest that precision demands and mental pressure increase upper extremity load, with mental pressure effects being larger than precision effects. The possible role of precision demands as an indirect mental stressor in working conditions is discussed.

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Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks.

The aim of this study was to assess the tasks and activities that make physical demands on Dutch fire-fighters and to compare them with a guideline related to the development of excessive fatigue. The occupational physical demands on Dutch fire-fighters were assessed by conducting a task analysis during 85 24-h shifts. While workplace observations on the duration and frequency of physical tasks and activities were recorded, the heart rate was measured. This was then used to calculate the heart rate reserve percentage (%HRR) for predefined working periods, tasks and activities during 24-h shifts. The findings indicate that actual fire-fighting during 24-h shifts is characterised by a low frequency of incidents, a short 'turn-out' time, short tasks, and activities with a moderate to occasionally high energetic workload. Two tasks which sometimes occur in actual fire-fighting exceeded the guideline on energetic workload. The conclusion was that, though the number of incidents and the occupational demands are low during 24-h shifts, the peak loads for these two tasks are energetically high and could lead to excessive fatigue. Consequently, attention may need to be paid to health surveillance for persons exposed to such energetic peak loads, the development of physical and medical selection procedures, training, and workplace adjustments.

/pdf/the-physical-demands-upon-dutch-fire-fighters-in-relation-to-225iysnf7v.pdf

The physical demands upon (Dutch) fire-fighters in relation to the maximum acceptable energetic workload

The effect of job rotation on the physical workload was investigated for male employees working at a refuse collecting department. Before the introduction of job rotation, an employee worked as a street sweeper, as a refuse collector or as a driver. After the introduction of job rotation, every employee was allowed to alternate between two of the three possible jobs during the day, i.e. refuse collecting/street sweeping, refuse collecting/driving or street sweeping/driving. Two non-rotation groups (i.e. refuse collectors and street sweepers) and two rotation groups (i.e. refuse collectors/street sweepers and street sweepers/drivers) were mutually compared. The physical workload was determined by measuring the perceived load, energetic load and postural load during a full working day. Job rotation resulted in a significant decrease of the perceived load and energetic load and a slight decrease of the postural load. The results indicate that the total amount of work performed by means of job rotation resulted in an overall reduced physical workload of the employees of the refuse collecting department.

Job rotation as a factor in reducing physical workload at a refuse collecting department

This study investigated the effect of work pace on workload, motor variability and fatigue during light assembly work. Upper extremity kinematics and electromyography (EMG) were obtained on a cycle-to-cycle basis for eight participants during two conditions, corresponding to "normal" and "high" work pace according to a predetermined time system for engineering. Indicators of fatigue, pain sensitivity and performance were recorded before, during and after the task. The level and variability of muscle activity did not differ according to work pace, and manifestations of muscle fatigue or changed pain sensitivity were not observed. In the high work pace, however, participants moved more efficiently, they showed more variability in wrist speed and acceleration, but they also made more errors. These results suggest that an increased work pace, within the range addressed here, will not have any substantial adverse effects on acute motor performance and fatigue in light, cyclic assembly work. STATEMENT OF RELEVANCE: In the manufacturing industry, work pace is a key issue in production system design and hence of interest to ergonomists as well as engineers. In this laboratory study, increasing the work pace did not show adverse effects in terms of biomechanical exposures and muscle fatigue, but it did lead to more errors. For the industrial engineer, this observation suggests that an increase in work pace might diminish production quality, even without any noticeable fatigue being experienced by the operators.

https://research.vu.nl/ws/files/3007231/Bosch%20Ergonomics%202011.pdf

Bart Visser

Papers

Pathophysiology of upper extremity muscle disorders

Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks.

The physical demands upon (Dutch) fire-fighters in relation to the maximum acceptable energetic workload

Job rotation as a factor in reducing physical workload at a refuse collecting department

The effect of work pace on workload, motor variability and fatigue during simulated light assembly work