Static Muscular Work Research Articles

Work-related musculoskeletal disorder and health risk behaviors in market-vendors: a mixed-methods study.

Work-related musculoskeletal disorders (WRMDs) are frequently observed among market vendors, and engaging in health risk behaviors can exacerbate these issues, leading to various health problems. Common health risk behaviors among market vendors include alcohol consumption and insufficient physical activity. However, there is currently a lack of research examining the prevalence of WRMDs and health risk behaviors among market vendors in Bangkok. Furthermore, the emerging trend of drug misuse within this group remains poorly understood. This study aims to explore the prevalence of muscle pain and flexibility issues and assess health risk behaviors, including alcohol consumption, inadequate exercise, and drug misuse, among market vendors. A mixed-method study was undertaken among 213 market vendors in Bangkok. Data collection utilized direct observation techniques, questionnaires, and muscle flexibility tests. Qualitative data were elucidated and showcased through textual descriptions and quotations. Quantitative data were analyzed using descriptive statistics to present numerical and percentage values. Qualitative findings revealed that market vendors often engage in static muscular work and maintain awkward postures due to their job characteristics and workstation setups. Quantitatively, the right arm was the most common pain region (34.7%), followed by the left leg (31.0%), right leg (30.0%), and left arm (28.6%). Additionally, 64.3% of participants showed poor muscle flexibility. The study also found that 35% of market vendors resorted to alcohol and 11.7% to drug misuse to cope with fatigue and prevent adverse symptoms. Moreover, 68.5% of participants reported no regular exercise due to lack of time. The study highlights the prevalence of musculoskeletal issues among market vendors, largely attributed to static muscular work and awkward postures dictated by their job roles and workstation arrangements. The right arm emerged as the most commonly affected area, followed by the left leg, right leg, and left arm, with significant rates of reported pain. The research also points to a notable lack of muscle flexibility in a majority of vendors and a concerning tendency towards alcohol and drug misuse as coping mechanisms for fatigue and symptom management. Furthermore, a significant portion of the vendors do not participate in regular exercise, primarily due to time constraints. These findings can be used to implement health prevention programs within the market vendor group.

ANÁLISE DE CONDUTAS E POSTURAS DOS ACADÊMICOS DE ODONTOLOGIA COM PREDISPOSIÇÃO À SÍNDROME DO TÚNEL DO CARPO

Carpal Tunnel Syndrome (CTS) is characterized by nerve compression that affects the upper limbs that can be caused by repetitive movements of the fist and fingers, extreme flexion and extension of the fist, forced contraction of the tendon that dislocate to the tunnel, static muscular work, vibrations, bad positioning during work activities and not in conformity to ergonomic patterns. These factors are common among Odontology professionals as many professionals present a loss of fist and fingers functionality, compromising the care of patients. The aim of this study is to detect and to analyze the methods and approaches used by Odontology professionals to carry out their activities and to guide them about the prevention of future STC with the distribution of informative material on stretching of the upper limbs. Questionnaires were applied to eighty dentistry students between the ages of 20 to 25 of the last year of the dentistry course from the UEPG and CESCAGE universities. These students were taking the disciplines of integrated clinic. In the sample, 45% (n = 36 students) were male and 55% (n = 44) were female. The variable in relation to the practice one of another professional activity had been searched, the symptoms mentioned in the questionnaire used in the study (Appendix I), in addition to specific tests (Tínel and Phalen). After treatment of the statistical data and follow up in the practical classes, it was observed that the STC symptoms prevail in female students with a predisposition to the syndrome. This can be explained as other activities were carried out at the same time of the practical activities and the ergonomic risk according to a check list for simplified evaluation of the risk of Repetitive Strain Injuries/Osteomuscular Disease Related of the Job occurrence. The results indicate a very high risk of RSI/DRJ.

A novel approach for determining fatigue resistances of different muscle groups in static cases

In ergonomics and biomechanics, muscle fatigue models based on maximum endurance time (MET) models are often used to integrate fatigue effect into ergonomic and biomechanical application. However, due to the empirical principle of those MET models, the disadvantages of this method are: 1) the MET models cannot reveal the muscle physiology background very well; 2) there is no general formation for those MET models to predict MET. In this paper, a theoretical MET model is extended from a simple muscle fatigue model with consideration of the external load and maximum voluntary contraction in passive static exertion cases. The universal availability of the extended MET model is analyzed in comparison to 24 existing empirical MET models. Using mathematical regression method, 21 of the 24 MET models have intraclass correlations over 0.9, which means the extended MET model could replace the existing MET models in a general and computationally efficient way. In addition, an important parameter, fatigability (or fatigue resistance) of different muscle groups, could be calculated via the mathematical regression approach. Its mean value and its standard deviation are useful for predicting MET values of a given population during static operations. The possible reasons influencing the fatigue resistance were classified and discussed, and it is still a very challenging work to find out the quantitative relationship between the fatigue resistance and the influencing factors. Relevance to industry MSD risks can be reduced by correct evaluation of static muscular work. Different muscle groups have different properties, and a generalized MET model is useful to simplify the fatigue analysis and fatigue modeling, especially for digital human techniques and virtual human simulation tools.

Evidence of reduced sympatho-adrenal and hypothalamic-pituitary activity during static muscular work in patients with fibromyalgia

To assess activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenocortical axis during static exercise in patients with fibromyalgia. Sixteen patients with fibromyalgia and 16 healthy controls performed a static knee extension until exhaustion. Plasma catecholamines, adrenocorticotropic hormone and cortisol, as well as blood pressure and heart rate, were assessed before, during and following contraction. Plasma C reactive protein was analysed at baseline. Blood pressure and heart rate increased during contraction (p < 0.001) and decreased following contraction (p < 0.001) in both groups alike. Compared with baseline, plasma catecholamines increased during contraction in both groups (p < 0.001), but patients with fibromyalgia had lower levels of plasma adrenaline (p < 0.04) and noradrenaline (p < 0.08) at all times. Adrenocorticotropic hormone increased at exhaustion in controls (p < 0.001), but not in patients with fibromyalgia, who also had lower adrenocorticotropic hormone at exhaustion (p < 0.02) compared with controls. There were no group differences, or changes over time in plasma cortisol. High sensitivity C reactive protein was higher in patients with fibromyalgia compared with controls (p < 0.02). Patients with fibromyalgia exhibited a hypoactive sympatho-adrenal system as well as a hypo-reactive hypothalamic-pituitary axis during static exercise.

Comparison of rest allowance models for static muscular work

Static muscular work associated with awkward postures with or without the application of force to an external object results in fatigue, discomfort, and musculoskeletal disorders. To prevent the effects of fatigue, sufficient and well-spaced rest periods are recommended. This paper presents an approach to determining rest periods for static muscular work in manufacturing workstations and compares the recommendations from four rest allowances models. The approach was applied to seven workstations in three industrial sectors: four workstations in the printing industry, one in the automotive industry and two in plant nurseries. The rest allowances proposed by the four models were compared with an estimation of rest allowances using the EN1005-3 standard. Results showed substantial differences in the recommendations from the different rest allowances models. Shoulder fatigue was the determining factor in the rest allowance for most workstations assessed. Caution should be exercised when using EN1005-3 to estimate rest allowances. Relevance to industry Static and intermittent static muscular work are known risk factors for work-related musculoskeletal disorders (WMSD). Determining appropriate work-rest regimens for static muscular work in industrial settings may be an efficient way to reduce this risk, but information to guide the selection of the most appropriate rest allowance model is lacking.

Percentile values for determining maximum endurance times for static muscular work

The maximum endurance time (MET) is a key parameter for the ergonomic evaluation of static work. The aim of this study is to offer practitioners MET values in relation to the %MVC (percentage of maximum voluntary contraction) that take into account the results of several studies published on MET. Twenty four published MET models were combined to extract MET percentile values that reflect the interindividual variability and differences among the experimental methods used to develop the models. The MET differences by muscle group are also verified. The results of this study show that, (1) there is a significant difference between the MET values for the back/hip and the MET values for the upper limbs, for a same %MVC value; (2) the model-generated MET values follow a lognormal distribution. A summary table is presented showing the most frequently used percentile values (5th, 10th and 15th percentiles) of the MET corresponding to a range of %MVC values. The data from this paper allow engineers and ergonomics practitioners to design workstations that can accommodate a desired proportion of the worker population, i.e., designs that are not restricted only to the 50th percentile. Relevance to industry Static and intermittent static muscular work is a known risk factor for musculoskeletal disorders (MSD). Estimation of MET to accommodate a percentage of the worker population is a necessary step in determining appropriate work-rest regimens for static muscular work in industrial settings.

A new table for work with a microscope, a solution to ergonomic problems

Microscope workers are exposed to continuous static muscular work and an increased risk of musculoskeletal disorders in the neck, shoulder and upper extremities. In a Finnish research centre, microscope workers reported pain in the shoulder, neck, lower back and upper back. As a consequence, a programme to solve the ergonomic problems of microscope work was initiated and led to the construction of a new table for microscopes. Ten experienced male microscope workers were chosen as subjects to carry out an experimental study in which the new table and an old one, an ordinary non-adjustable laboratory table, were compared in a standardized microscope task. The dependent variable was the electromyographic activity measured from muscles in the neck–shoulder region. The new table allowed the microscope to be used with the head in an upright position, the forearms supported and with less flexion of the upper arm. Surface electromyographic measurements also confirmed that the changes were ergonomic improvements.

Analytic Method by Muscular Electric Potential for Static Muscular Work in Agricultural Production

Analytic Method by Muscular Electric Potential for Static Muscular Work in Agricultural Production

Dependence of mean duration of heart period and of arrhythmia during dynamic muscular work on the greatness and differences of work load and during static muscular work on the greatness of work load (author's transl)

Mean duration of heart period (DHP chi) and its standard deviation (SD), indicating heart arrhythmia and significantly correlating with DHP chi, decreased with stepwise increase of dynamic muscular work on a bicycle ergometer and static muscular work of the right upper arm flexor beyond the limit of permanent performance. This correlation, however, can be understood globally only, since the decrease of DHP chi and SD was not always continuous, but frequently changing, with alterations of increase and decrease from step to step of dynamic work load and from minute to minute of static muscular strain. This concerned particularly SD. A continuous decrease of DHP chi in dynamic muscular work was obtained only by load differences of 40 W, not by differences of 10 or 20 W. A more continuous decrease of SD was also noted during greater load-differences. The significant correlation of DHP chi and SD was lost at a load-difference of 10 W on the 60 W-step and at a load-difference of 40 W on the 180 W-step. Great loads caused at the same load-step less frequent variations of DHP chi, not of SD, than little loads. If no preceding work took place, a contary reaction of DHP chi and SD was noted often at the first load-step. Static work with greater holding force caused a more continuous decrease of DHP chi, in a lower degree of SD, than static work with lower holding force. DHP chi decreased mainly in the first minute of strain. The adjustment of mean heart rate and heart arrhythmia on a level corresponding to increase of load is influenced essentially by the difference of muscular strain appearing between two periods of work load or periods of holding. The regulation of the mean duration of heart period and of heart arrhythmia does not necessarily depend on each other.

Problems in determining rest allowances: Part 1: Use of modern methods to evaluate stress and strain in static muscular work

After mentioning today's practice in handling the problem of setting rest allowances, definitions are given for the terms of fatigue, recovery and degree of fatigue. Discriminating between stress and strain leads to the possibilities in determining both. Measurable effects of fatigue in static muscular work are discussed. The procedure for determining optimal working rhythms by measuring stress and strain in static muscular work is explained.

Respiratory responses to static muscular work

The respiratory responses to sustained hand-grip contraction at four tension levels, graded in per cent of maximal voluntary contraction (MVC), were investigated. An increased ventilation was always observed prior to the work, and explained as an element in the alarm-defense reaction. The typical response pattern during and after work was a steady increase during contractions above the 20% MVC level. The ventilatory peak was observed at the end of the work, then a gradual return to resting level took place during the recovery period. A hyperventilation took place at tensions above the 20% MVC level. The chemical environment of the contracted muscles was altered, as is evident from the finding of lowered venous pH and P V O 2 , and elevated P V O 2 and lactate concentration. The level of blood gases in arterial blood remained unchanged, and a nervous reflex mechanism in addition to cortical influence is proposed as an explanation of the hyperventilation.

Heart rate and the concept of circulatory load.

The functional demands of different types of work-load (dynamic and static muscular work, exposure to extreme hot or cold climates and the mental load caused by emotional stress and by the processing of information) are discussed in this paper. The need for absolute and comparative or relative measurement or estimation of these functional physiological demands in different work situations are considered. The validity of oxygen consumption of the body and of heartrate as an integral ergonomics measure are critically discussed. It is pointed out that these measures have only a high validity when (heavy) dynamic muscular work is considered. However, in muscular work of a static type and in the other type3 of work-load mentioned (climatic and mental conditions) there are many restrictions on their validity Moreover, from the point of view of occupational medicine and ergonomics there is a need for specific knowledge about the load of different organic (functional) systems. Therefore, the concept of circulator...

Influence of Dynamic and Static Muscular Work on Red Blood Cell

Influence of Dynamic and Static Muscular Work on Red Blood Cell

THE WORK CAPACITY OF A SYNERGIC MUSCULAR GROUP

A new conception of dynamic or static muscular work tests is presented. The authors define the critical power of a muscular work from the notions of maximum work and maximum time of work. The work capacity is then considered in the case of dynamic work, and of continuous or intermittent static work. From the data presented it is possible to define the maximum amount of work that can be performed in a given time as well as the conditions of work performed without fatigue

Recording of CTG at Heavy Static Muscular Work by Wireless Telemetry

Recording of CTG at Heavy Static Muscular Work by Wireless Telemetry

Application of static muscular contraction to the analysis of the mechanism of vomiting

Static muscular work which consisted in holding a load on the back inhibited the act of vomiting which was induced by apomorphine or by stimulation of the stomach receptors by a solution of potassium chloride. The act of vomiting was inhibited by placing the dog under conditions in which the experiment was formerly conducted (following several experiments with the load, i.e., by way of conditioned reflex). Various components of the act of vomiting were inhibited differently. The mildest depression was found in the activity of somatic musc les (abdominal press). The autonomic component of the act of vomiting (secretion of saliva, dyspnea, stomach contraction, increased rate of cardiac contractions) was only slightly inhibited. With increase of inhibition (anesthesia) the reactions of blood pressure and respiration were found to be the most stable components out of the whole autonomic complex of vomiting reactions. A definite sequence of introduction of various components of the act of vomiting was established in experiments without the load. Several new suggestions are made concerning the regulation of the act of vomiting.