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Effects of two recovery methods on the leg muscle fatigue of oceanauts in a manned submersible

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Chen D., Zhu M., Fan Y., Wang J.
Medycyna Pracy
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2022
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vol. 73
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issue 2
95-107
EN
The cabin of the manned submersible is a narrow and sealed space. The long-time work of oceanauts is easy to cause muscle fatigue and stiffness, which reduces efficiency. This paper explored the relative more effective way to relieve leg muscle fatigue of the oceanauts in the manned submersible.Material and MethodsTwenty healthy young people with an average age of 24 years were selected as the participants, while the usual natural relaxation and the stretching method proposed by the surveys were selected as the relieve method for muscle fatigue. This study compared the effects of the 2 recovery ways using the electromyography data from the quadriceps femoris and biceps femoris, and the subjective scales.ResultsWith the support of data of integral electromyogram (iEMG), root-mean-square (RMS), subjective scales, authors finally found that the 2 muscles of the leg are fatigued significantly, and biceps femoris has more accumulation of fatigue. Although the 2 recovery ways have a significant relief effect on muscle fatigue, the stretching method can reduce more muscle fatigue in a short period of time, especially for biceps femoris. The stretching method is advocated for the oceanauts.ConclusionsThe findings suggested that the stretching method was optimal for relieving the muscle fatigue of the oceanauts during the operation. Med Pr. 2022;73(2):95–107
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Changes in blood morphology and chosen biochemical parameters in ultra-marathon runners during a 100-km run in relation to the age and speed of runners

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Jastrzębski Z., Żychowska M., Jastrzębska M., Prusik K., Prusik K., Kortas J., Ratkowski W., Konieczna A., Radzimiński Ł.
International Journal of Occupational Medicine and Environmental Health
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2016
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vol. 29
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issue 5
801-814
EN
Objectives The objective of the study was to reveal morphology, electrolyte and chosen biochemical parameters in terms of health risk in runners in reference to their age and running speed in the case of running a distance of 100 km, which occur after 12 h or 24 h of recovery. Material and Methods Fourteen experienced, male, amateur, ultra-marathon runners, divided into two age and two speed groups took part in the 100-km run. Blood samples for analyses indexes were collected from the ulnar vein just before the run, after 25 km, 50 km, 75 km and 100 km, as well as 12 h and 24 h after termination of the run. Results The sustained ultramarathon run along with the distance covered (p < 0.05) caused an increase in myoglobin (max 90-fold), bilirubin (max 2.8-fold) and total antioxidant status (max 1.15-fold), which also continued during the recovery. Significant changes in the number of white blood cells were observed with each sequential course and could be associated with muscle damage. The electrolyte showed changes towards slight hyperkalemia, but no changes in natrium and calcium concentrations. There were no significant differences between the age and speed groups for all the parameters after completing the 100-km run as well as after 12 h and 24 h of recovery. Conclusions Considering changes in blood morphology and chosen biochemical parameters in ultra-marathon runners during a 100-km run it can be stated that such an exhausting effort may be dangerous for human health due to metabolic changes and large damage to the organs. Negative metabolic changes are independent of age of an ultramarathon runner and occur both in younger (32±5.33 years) and older participants (50.56±9.7 years). It can be concluded that organ damage and negative metabolic changes during a 100-km run occur similarly in participants less experienced as well as in well trained runners. Int J Occup Med Environ Health 2016;29(5):801–814
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Shoulder girdle muscle activity and fatigue in traditional and improved design carpet weaving workstations

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Allahyari T., Mortazavi N., Khalkhali H. R., Sanjari M. A.
International Journal of Occupational Medicine and Environmental Health
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2015
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vol. 29
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issue 2
345-354
EN
Objectives Work-related musculoskeletal disorders in the neck and shoulder regions are common among carpet weavers. Working for prolonged hours in a static and awkward posture could result in an increased muscle activity and may lead to musculoskeletal disorders. Ergonomic workstation improvements can reduce muscle fatigue and the risk of musculoskeletal disorders. Material and Methods The aim of this study is to assess and to compare upper trapezius and middle deltoid muscle activity in 2 traditional and improved design carpet weaving workstations. These 2 workstations were simulated in a laboratory and 12 women carpet weavers worked for 3 h. Electromyography (EMG) signals were recorded during work in bilateral upper trapezius and bilateral middle deltoid. The root mean square (RMS) and median frequency (MF) values were calculated and used to assess muscle load and fatigue. Repeated measure ANOVA was performed to assess the effect of independent variables on muscular activity and fatigue. The participants were asked to report shoulder region fatigue on the Borg’s Category-Ratio scale (Borg CR-10). Results Root mean square values in workstation A are significantly higher than in workstation B. Furthermore, EMG amplitude was higher in bilateral trapezius than in bilateral deltoid. However, muscle fatigue was not observed in any of the workstations. Conclusions The results of the study revealed that muscle load in a traditional workstation was high, but fatigue was not observed. Further studies investigating other muscles involved in carpet weaving tasks are recommended.
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Assessment of shoulder and low back muscle activity of male kitchen workers using surface electromyography

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Subramaniam S., Murugesan S., Jayaraman S.
International Journal of Occupational Medicine and Environmental Health
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2017
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vol. 31
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issue 1
81-90
EN
Objectives: This study aims to assess muscle fatigue for kitchen workers during various tasks in a kitchen. Material and Methods: This study consists of 2 phases: a) surface electromyography (EMG) to determine muscle fatigue of trapezius and erector spinae muscles bilaterally for 12 healthy male volunteers during 30 min of Indian flatbread (chapati) preparation, b) self-administered questionnaire study after 30 min preparation to determine the impact on performance. Results: Surface EMG results show that the right trapezius muscle had significantly higher fatigue during kneading, rolling and roasting tasks. Similarly, right erector spinae muscle showed significantly higher fatigue during rolling and roasting tasks. Conclusions: Both phases of the study conclude that, even though the dynamic postural adjustment may reduce fatigue during the work schedule; the combination of risk factors like the repetitive task, forceful exertion and prolonged standing during working results in a high risk of developing muscle fatigue. Int J Occup Med Environ Health 2018;31(1):81–90
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Shoulder girdle muscle activity and fatigue during automobile chassis repair

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Tian B., Yu S., Chu J., Li W.
International Journal of Occupational Medicine and Environmental Health
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2019
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vol. 32
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issue 4
537-552
EN
Objectives The objective of this study was to assess the postures that were commonly used in automobile chassis repair operations, and to evaluate shoulder girdle muscle fatigue for different combinations of the weight of hand-tools. Material and Methods Two right muscles, including upper trapezius (UT) and middle deltoid (MD), were selected. Surface electromyography (SEMG) and a perceived level of discomfort (PLD) were used to assess the degree of shoulder girdle fatigue. Fifteen healthy young male subjects from the Northwestern Polytechnical University participated in the test. The test consisted of assuming 4 different postures and maintaining each of them for 60 s. The 4 postures varied in terms of dumbbell weights, standing for the hand-tools weight: W1 was 0.48 kg and W2 was 0.75 kg; the 4 shoulder postures were shoulder flexions of 150°, 120°, 90°, and 60°, combined with an included elbow angle of 180°, 150°, 120° and 90°, respectively. The experimental sequences were randomly selected. The signals of SEMG and the values of PLD in the shoulder girdle were recorded in 60 s. All subjects completed the whole test. The repeated measure analysis of variance (ANOVA) was performed to ascertain differences between dumbbell weight (0.48 kg and 0.75 kg) and shoulder postures (150°/180°, 120°/150°, 90°/120° and 60°/90°). The Friedman test was utilized to determine the significant differences for UT(PLD) and MD(PLD) on shoulder postures. Spearman’s correlation was used to analyze the relationship between the subjective and objective measurements. Results Significant correlational relationships existed between the UT percentage of the maximal voluntary electrical activation (%MVE) and UT(PLD) (r = 0.459, p < 0.01), between MD(%MVE) and MD(PLD) (r = 0.821, p < 0.01). The results showed that SEMG and PLD of the 4 postures under analysis differed significantly (p < 0.05). Conclusions It was indicated that posture T4 (shoulder forward flexion 60° and included elbow angle 90°) resulted in the lowest fatigue, both in terms of the objective measure and the subjective perception, which meant that this posture was more ergonomic. Int J Occup Med Environ Health. 2019;32(4):537–52
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A method for designing the longitudinal position of a porthole in a manned submersible based on the back muscle fatigue characteristics

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Zhu M., Chen D., Fan Y., Guo J.
International Journal of Occupational Medicine and Environmental Health
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2021
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vol. 34
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issue 6
701-721
EN
ObjectivesThe proper porthole angle contributes to relieving the operation fatigue and improving the efficiency of oceanauts. In this study, the authors explored the effect of 3 different porthole longitudinal positions on the oceanauts’ back muscles using surface electromyography (sEMG) analysis, and the characteristics of the perceived body comfort was obtained.Material and MethodsOverall, 40 healthy participants were recruited to perform tasks in a simulated cabin environment. Electromyographic (EMG) signals were recorded from the trapezius medius, lower trapezius, and erector spinal muscles for porthole angles of –5°, –15°, and +15°, relative to the horizontal line of sight during a 21-minute experiment. The subject comfort scores were collected at 7, 14 and 21 min. The integrated electromyogram (iEMG) and the root mean square (RMS) of EMG signals, as well as the mean power frequency (MPF), and the mean frequency (MF) were calculated.ResultsThe subjective scores of the +15° porthole at each stage of work are higher than those of the –15° and –5° portholes. The results of iEMG, RMS, MF and MPF all indicated that the +15° porthole design was more conducive to lowering the rate of muscle fatigue, while the –5° and –15° portholes increased the muscle fatigue rate and led to greater fatigue. It was found that the lower trapezius was more prone to fatigue than the trapezius medius and erector spinal muscles. The height, weight and body mass index of the participants were found to negatively correlate with muscles at the +15° porthole, which is highly consistent with the actual situation.ConclusionsThe findings suggested that the +15° position was optimal for delaying the muscle fatigue of the participants and for improving the work efficiency of oceanauts.
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