• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.188-202
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• 2004

This research was designed to investigate biomechanical aspects of the evolution based on the hypothesis of dynamic cooperative interactions between the locomotion pattern and the body shape in the evolution of human bipedal walking The musculoskeletal model used in the computer simulation consisted of 12 rigid segments and 26 muscles. The nervous system was represented by 18 rhythmic pattern generators. The genetic algorithm was employed based on the natural selection theory to represent the evolutionary mechanism. Evolutionary strategy was assumed to minimize the cost function that is weighted sum of the energy consumption, the muscular fatigue and the load on the skeletal system. The simulation results showed that repeated manipulations of the genetic algorithm resulted in the change of body shape and locomotion pattern from those of chimpanzee to those of human. It was suggested that improving locomotive efficiency and the load on the musculoskeletal system are feasible factors driving the evolution of the human body shape and the bipedal locomotion pattern. The hypothetical evolution method employed in this study can be a new powerful tool for investigation of the evolution process.

• Journal of Dental Anesthesia and Pain Medicine
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• v.19 no.1
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• pp.67-72
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• 2019

Myasthenia gravis (MG) is a neuromuscular autoimmune disorder which clinically presents as muscular weakness and fatigue due to autoantibody formation against acetylcholine receptors (AChR), leading to their subsequent destruction. Due to the neuromuscular implications of MG, certain considerations must be taken into account when providing anesthesia to MG patients. In the following case report, we have outlined procedural considerations for the anesthetic management of a patient with MG undergoing deep sedation for an elective oral surgery in an outpatient setting, as well as a discussion of relevant literature.

• Journal of the Korean Society of Systems Engineering
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• v.20 no.spc1
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• pp.76-89
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• 2024

This study investigates the impact of standardized underground logistics conainers on lower body muscle activation during warehouse tasks, comparing conventional roll containers(A type) with newly developed ones(B type). Through a detailed experimental setup involving electromyography(EMG) and tensiomyography(TMG), muscle activities of the lower limbs were quantitatively analyzed during loading unloading and transporting tasks. Results indicated no significant difference in muscle activation patters between the two rolltainer types, suggesting that the dimensions of these containers do not critically affect the muscular strain and workload. Furthermore, the TMG analysis revealed that muscle contraction velocity(Vc) increased in certain muscles when using the B-type rolltainer, indicating a potential for more efficient muscle engagement without increasing fatigue. This research underscores the importance of ergonomic considerations in the design of logistics equipment and suggests that further studies should focus on optimizing the interaction between human operators and logistical systems to enhance safety and efficiency in warehouse operations.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.141-147
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• 2015

Objective : This study aimed to understand how increased heart rates at the time of drop landing during a step test would affect biomechanical variables of the lower extremity limbs. Background : Ballet performers do more than 200 landings in a daily training. This training raises the heart rate and the fatigability of the lower extremity limbs. Ballet performance high heart rate can trigger lower extremity limb injury. Method : We instructed eight female ballet dancers with no instability in their ankle joints(mean ${\pm}$ SD: age, $20.7{\pm}0.7yr$; body mass index, $19.5{\pm}1.2kg/m^2$, career duration, $8.7{\pm}2.0yr$) to perform the drop landing under the following conditions: rest, 60% heart rate reserve (HRR) and 80% HRR. Results : First, the study confirmed that the increased heart rates of the female ballet dancers did not affect the working ranges of the knee joints during drop landing but only increased angular speeds, which was considered a negative shock-absorption strategy. Second, 80% HRR, which was increased through the step tests, led to severe fatigue among the female ballet dancers, which made them unable to perform a lower extremity limb-neutral position. Hence, their drop landing was unstable, with increased introversion and extroversion moments. Third, we observed that the increasing 80% HRR failed to help the dancers effectively control ground reaction forces but improved the muscular activities of the rectus femoris and vastus medialis oblique muscles. Fourth, the increasing heart rates were positively related to the muscular activities of the vastus medialis oblique and rectus femoris muscles, and the extroversion and introversion moments. Conclusion/Application : Our results prove that increased HRR during a step test negatively affects the biomechanical variables of the lower extremity limbs at the time of drop landing.

• Journal of Embryo Transfer
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• v.23 no.4
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• pp.283-289
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• 2008

Lepidium meyenii, known as Maca, is traditionally employed in the Andean region for its supposed properties to improve energy and fertility. In the present study, we investigated the effects of gelatinized and fermented Maca on improvement of physical stamina and epididymal sperm counts, and on blood biochemical parameters related to fatigue and tissue injury: creatine phosphokinase, aspartate transaminase, lactate dehydrogenase, blood urea nitrogen, glucose, total cholesterol and total proteins. Adult male mice was divided at random into two main groups (resting and excercise groups). The excercise group was separated into three subgroups (exercise only, exercise with gelatinized Maca and fermented Maca-treatment groups). Gelatinized or fermented Maca (800 mg/kg) were orally administered for 30 days. All animals in exercise groups were subjected to daily 30-min swimming for 28 days 30 min after Maca treatment. Daily exercise decreased the body weight gain, and fermented Maca further attenuated the body weight increase. Gelatinized and fermented Maca significantly increased the maximum swimming time on 14 and 28 days of treatment (p<0.05), respectively, suggestive of a long-term stamina-enhancing effect of fermented Maca. Both Maca fully or significantly recovered blood parameters of energy as well as muscular and hepatocytic injuries changed by repeated exercise and maximum swimming performance (p<0.01). Moreover, gelatinized and fermented Maca increased epididymal sperm counts 22.0% and 32.0%, respectively. In conclusion, the results indicate potential benefits of Maca for improving both physical stamina by minimizing muscular and hepatic damage and preserving energy during swimming exercise and male reproductive function by increasing epididymal sperm counts.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.4
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• pp.550-561
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• 2019

Objectives: The purpose of this study is to provide basic data for the improvement of the working environment for health prevention and related countermeasures for shift workers. This study was conducted based on the Fifth Korean Working Conditions Survey (KWCS), which analyzed the health effects of shift work forces and compared them with preceding studies. Methods: By analyzing secondary rates using raw data from the 5th KWCS, 4,870 (9.7%) of the 50,184 total study subjects were divided into shift work and 45,314 (90.3%) non-shift work groups based on the response to shift status. Variables that could affect work health issues were identified and corrected. A cross-analysis was conducted to examine demographic characteristics (gender, age, and education level) of the workers and occupation characteristics (monthly net earnings, employment type, occupation, working period up to now, workplace scale, type of work system, and weekly working hours). In order to find the work health issue ratio between the shift and non-shift work groups, logistic regression was analyzed and the association with health problems according to shift type by gender was looked at through cross-analysis. Results: According to the surveys conducted from the 1st KWCS (2006) to the 5th KWCS (2017), the proportion of shift workers continued to increase. Also, muscular pains in the lower limbs (hips, legs, knees, feet, etc.) (OR=1.135, 95%CI 1.031-1.251), headaches, eyestrain (OR=1.580, 95% CI 1.428-1.748), anxiety (OR=1.715, 95% CI 1.402-2.099), difficulty falling asleep (OR=1.391), and other problems (OR=7.392) were reported. In addition, back pain, muscular pains in shoulders, neck and/or upper limbs, muscular pains in lower limbs (hips, legs, knees, feet, etc.), headaches, eyestrain, depression, anxiety, overall fatigue resulted in significant results for both male and female shift workers. Depression and anxiety were higher in female shift/circulation compared to males. Conclusions: The social nets for the health and safety of shift workers should be explored in a variety of ways, including management and supervision of shift sites, attempts to reorganize and improve the shift system, development of workers' health recovery programs, promotion, systematic treatment, and compensation systems.

• Korean Journal of Applied Biomechanics
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• v.32 no.3
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• pp.94-102
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• 2022

Objective: The purpose of this study was to investigate the effect of acute transcranial direct current stimulation (tDCS) on the isokinetic muscular endurance of the lower extremity for young adults. Method: Thirteen young adults performed isokinetic fatigue tasks for two experimental conditions including real tDCS and sham stimulation protocols. Before and after the task, the tensiomyography was used for evaluating muscle contraction characteristics of vastus medialis and semitendinosus. Paired t-test was performed to compare the fatigue index, changes in maximum radial displacement (∆Dm), delay time (∆Tc), and velocity of contraction (∆Vc) between tDCS conditions. Results: We found no significant differences in the fatigue index between real and sham conditions. In addition, the analyses identified no significant different values of ∆Dm, ∆Tc, and ∆Vc in the vastus medialis and semitendinosus between real and sham conditions. Conclusion: These findings suggest that the tDCS protocols may have no acute effect on lower limb muscle endurance for young adults. Future studies should consider the long-term effects of repetitive tDCS sessions, various stimulation positions, exercise tasks, and participant characteristics to more clearly understand the effect of tDCS on muscle endurance of lower extremities.

• Fashion & Textile Research Journal
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• v.20 no.3
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• pp.343-352
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• 2018

The objective of this study is to investigate the market of fitness compression wear as well as to design an optimal fitness compression wear by analyzing the muscle and movement characteristics of the elderly women in Korea. In this regard, research for functional garments is needed to increase muscle activity of elderly people during physical exercise. Firstly, we investigated the brand, design, size, material, and pattern of fitness wear based on the market survey. Secondly, we identified preference, evaluation items, evaluation method, and pattern design method based on the literature review. Finally, in addition, the motion type, range, angle to improve the muscle strength of the elderly were investigated and the maximum muscle strengths of each motion were analyzed by using 2007 Size Korea data (n = 386). It is also designed for muscle fatigue through exercise and rapid fatigue recovery after exercise. The evaluation methods for fitness compression wear were classified as motor functionality, physiological comfort, pattern and material suitability evaluations. The muscle strength at leg (pushing force) and waist (lifting force) of the ages of 60 to 69 years old showed 239.3 N and 274.5 N, respectively, which were the lowest forces compared to younger age groups. By applying these results to the design process of fitness wear, it is anticipated that the fitness wear will have a proper fit to the body shape of elderly people in South Korea as well as it can increase muscle efficiency to promote physical capability and healthy life for senior people.

• Nutritional Sciences
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• v.8 no.3
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• pp.189-195
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• 2005

To assess the effect of pinitol supplementation and strength training for two weeks on the anaerobic capacity during and after exercise, and improvement of glucose metabolism during the recovery period of muscular fatigue with repeated acute bouts of cycling exercise, a total of 24 healthy young men were recruited and randomly and equally divided into three groups; pinitol supplementation group (PSG), placebo group (PLG), and control group (CON). Using a randomized double-blinded design, subjects in PSG were provided pinitol supplement, consumed orally 1.2 g/day, and participated in the resistance exercise program and cycling exercise for two weeks. Subjects in PLG underwent the same protocol as those in PSG but consumed the same amount of placebo. No supplementation and exercise program was given to CON. Before and after the intervention, all subjects were tested for their anaerobic capacities evaluated by Wingate test twice separated by 30 min. During the test, peak anaerobic power (PP), mean anaerobic power, total work, and fatigue index were evaluated During resting and recovery, blood samples were drawn and plasma pinitol, myo-inositol, chiro-inositol, insulin, free fatty acid, glucose, and lactate levels were analyzed After two weeks, PP and relative PP of the second biking were improved from the first biking in PSG only (p<0.05). No changes were found in all other variables of Wingate test in all groups. No statistical differences between groups and pre- and post-intervention were observed in concentrations of pinitol, myo-inositol, and chiro-inositol, but pinitol concentration was higher during recovery compared to the baseline in all groups and testings (p<0.05). Lactate level during recovery was higher than the resting level, but no other blood parameters were significantly changed. In conclusion, two weeks of pinitol supplementation in conjunction with short duration of anaerobic training in healthy young men did not induce any obvious benefits in terms of anaerobic capacity and energy metabolism Individual and/or population susceptibility may be one factor responsible for adopting pinitol supplementation.

• Safety and Health at Work
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• v.11 no.2
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• pp.207-214
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• 2020

Background: Prolonged sitting at work can lead to adverse health outcomes. The health risk of office workers is an increasing concern for the society and industry, with prolonged sitting work becoming more prevalent. Objective: This study aimed to explore the variation in muscle activities during prolonged sitting work and found out when and how to take a break to mitigate the risk of muscle symptoms. Methods: A preliminary survey was conducted to find out the prevalence of muscle discomfort in sedentary work. Firstly, a 2-h sedentary computer work was designed based on the preliminary study to investigate the variation in muscle activities. Twenty-four participants took part in the electromyography (EMG) measurement study. The EMG variations in the trapezius muscle and latissimus dorsi were investigated. Then the intervention time was determined based on the EMG measurement study. Secondly, 48 participants were divided into six groups to compare the effectiveness of every break type (passive break, active break of changing their posture, and stand and stretch their body with 5 or 10 mins). Finally, data consisting of EMG amplitudes and spectra and subjective assessment of discomfort were analyzed. Results: In the EMG experiment, results from the joint analysis of the spectral and amplitude method showed muscle fatigue after about 40 mins of sedentary work. In the intervention experiment, the results showed that standing and stretching for 5 mins was the most effective break type, and this type of break could keep the muscles' state at a recovery level for about 30-45 mins. Conclusions: This study offers the possibility of being applied to office workers and provides preliminary data support and theoretical exploration for a follow-up early muscle fatigue detection system.