• Journal of Korea Society of Industrial Information Systems
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• v.5 no.2
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• pp.1-8
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• 2000

Manual material handling(MMH)is major factor which causing physical injuries of worker at working area and frequency of low back pain(LBP) is increasing industrial accidents. Especially, working in bad circumstance such as farm, orchard, harbor loading and unloading, logging place and mining place which located in inclined slope can cause much possibility of hazard and absence of working balance can cause injuries of musculoskeletal system such as joint, bone, ligament. So, this study used EMG system to measure and evaluate muscle force information and fatigue of worker when lifting on slope. The result of measuring averaged integrated EMG(AEMG) shows multifidus muscle be used more than anything else in force. neck extensors are used at 15°, 20°frequently. generally the AEMG result shows multifidus muscle be used in force. Commonly, muscle fatigue of multifidus is higher than other muscle by analysis mean power frequency(MPF). The result of load sharing rate shows multifidus and erectorspinae which are deep spinal muscles is relatively high and neck extensor is low.

• Animal Bioscience
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• v.34 no.8
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• pp.1375-1381
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• 2021

Objective: This study was conducted to determine the effect of freeze-thawed cycles (Fresh meat, F-T 1 cycle and F-T 2 cycles) on the quality characteristics of porcine longissimus dorsi muscle. Methods: A total of 20 three-crossbred pigs (Duroc×[Large White×Landrace]) were randomly obtained from a commercial slaughterhouse in Thailand. Muscle samples were immediately taken from 10 to 11th of the longissimus dorsi for histochemical analysis. The muscles were cut into 2.54 cm-thick chops. A minimum of 20 chops were used for each treatment (fresh meat, freeze-thawed 1 and 2 cycles). Individually chops were packaged in polyethylene bags and frozen at -20℃ for 6 months followed by thawing in refrigerator at 4℃ for 24 h (the 1st freeze-thawed cycle). The freeze-thawed procedure was repeated for two cycles (the 2nd freeze-thawed cycle). Thawing loss, shear force value, citrate synthase activity and muscle fiber characteristics were determined on the muscles. Results: Results showed that increasing of freeze-thawed cycle increased the thawing loss (p<0.01) and citrate synthase activity (p<0.001). Shear force value of fresh meat was higher than freeze-thawed 1 and 2 cycles (F-T 1 cycle and F-T 2 cycles). Freeze-thawed cycles affected muscle characteristics. Muscle fiber area and muscle fiber diameter decreased with an increasing number of freeze-thawed cycles (p<0.001), while the thickness of endomysium and perimysium were increased (p<0.001). Conclusion: Repeated freeze-thawed cycles degraded muscle fiber structure and deteriorated pork quality.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.117-122
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• 2010

Purpose: The purpose of this study was to measure the active force of extraocular muscles on mono- and binocular movements for 62 healthy koreans (male: 29, female: 33). Methods: The force of adduction, abduction, elevation and depression, of right and left eye on monocular movement were tested with horizontal moving distance based on corneal limbus and the force of superior oblique muscle and inferior oblique muscle on binocular movement were measured with vertical moving distance between corneal limbus. The distances were obtained by high resolution digital image processing. Results: At monocular movements of tested subjects. the power of abduction, adduction, elevation and depression of right and left eye were (male) 9.35 nun, 9.75 mm, (female) 9.02 mm, 9.52 mm, (male) 10.23 mm, 10.16 mm, (female) 10.17 mm, 10.07 mm, (male) 7.01 mm,6.91 mm, (female) 6.98 mm, 6.64 mm, (male) 7.52 mm, 6.82 mm, (female) 7.52 mm, 6.67 mm, respectively. The active force of binocular movements were 54.8% hyperergasia and 45.1% hypergasia/67.7% hyperergasia and 32.2% hypergasia with inferior oblique muscle, 64.5% hyperergasia and 35.5% hypergasia/58.1% hyperergasia and 41.9% hypergasia with superior oblique muscle, respectively. Conclusions: The force of horizontal movement was higher than vertical movement. The value of adduction was higher than abduction on horizontal movement, and the value of depression was higher than elevation on vertical movement. In the both of inferior and superior oblique muscle, the ratio of hyperergasia was higher than that of hypergasia.

• Physical Therapy Korea
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• v.4 no.2
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• pp.1-9
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• 1997

Skeletal muscle fatigue is often associated with diminished athletic performance and inability to maintain an expected force output as a function of time. The purpose of this study was to compare the effect of duration of exercise on skeletal muscle fatigue between Weight Lifters(WL) and Non-Weight Lifters(NWL). There were twelve normal healthy adult volunteers, ranging in age from 18 to 35 years. The group consisted of six NWL and six WL. Randomized cross-over design was set up and work-rest cycle was 8 minutes work and 1 minute rest based on 15% MVC. Muscle fatigue was measured by the amount of force produced by the wrist flexor muscle and EMG amplitude over time. Repeated measures ANOVAs($2{\times}4$) were used to determine two types of subjects(WL, NWL) during four different duration of exercises(16, 32, 48, 64 minutes). The force decreased over time in NWL and WL, but there was no significant difference(F=2.83, p>0.05). However, the EMG amplitude increased in WL(0.8200) and NWL(0.6348). The WL exhibited an increase in EMG at the end of the period, especially at 48 minutes of exercises than did the NWL(F=9.58, p<.05). This suggests the WL were able to adjust to prolonged effort with adaptations in neural effect over time, resulting in higher EMG amplitude. That is, WL may be able to learn to recruit more motor units with training. It is important to the degree of neuromuscular fatigue and the time needed for recovery may differ considerably between WL and NWL, there is a need to plan proper strength training or rehabilitation protocols to match with the requirements in different characteristics of groups.

• Journal of Biomedical Engineering Research
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• v.44 no.5
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• pp.336-345
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• 2023

The present study was designed to evaluate changes in neuromuscular properties and the structural and qualitative characteristics of muscles during submaximal isometric contractions at low-to-relatively vigorous target forces and to determine their influence on force steadiness (FS). Thirteen young adult males performed submaximal isometric knee extensions at 10, 20, 50, and 70% of their maximal voluntary isometric contraction using their non-dominant legs. During submaximal contractions, we recorded force, EMG signals from vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF), and ultrasound images from the distal RF (dRF). Force and EMG standard deviation (SD) and coefficient of variation (CV) values were used to measure FS and EMG steadiness, respectively. Muscle thickness (MT), pennation angle (PA), echo intensity (EI), and texture features were calculated from ultrasound images to assess the structural and qualitative characteristics of the muscle. FS, neuromuscular properties, and texture features showed significant differences across different force levels. Additionally, there were significant differences in EMG_CV among the quadriceps at the 50% and 70% force levels. The results of correlation analysis revealed that FS had a significant relationship with EMG_CV in VM, VL, and RF, as well as with the texture features of dRF. This study's findings demonstrate that EMG steadiness and texture features are influenced by the magnitude of the target force and are closely related to FS, indicating their potential contribution to force output control.

• Journal of Biomedical Engineering Research
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• v.26 no.5
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• pp.257-264
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• 2005

This paper proposes an ionic polymer metal composite (IPMC) based artificial muscle to be applicable to the Myoelectric hand prosthesis. The IPMC consists of a thin polymer membrane with metal electrodes plated chemically on both faces, and it is widely applying to the artificial muscle because it is driven by relatively low input voltage. The control commands for the IPMC-based artificial muscle is given by electromyographic (EMG) signals obtained from human forearm. By an intended contraction of the human flexor carpi ulnaris and extensor carpi ulnaris muscles, we investigated the actuation behavior of the IPMC-based artificial muscle. To obtain higher actuation force of the IPMC, the single layered as thick as $800[{\mu}m]$ or multi-layered IPMC of which each layer can be as thick as $178[{\mu}m]$ are prepared. As a result, the bending force was up to the maximum 12[gf] from 1[gf] by actuating the single layered IPMC with $178[{\mu}m]$, but the bending displacement was reduced to 6[mm] from 30[mm]. The experimental results using an implemented IPMC control system show a possibility and a usability of the bio-mimetic artificial muscle.

• Physical Therapy Rehabilitation Science
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• v.10 no.2
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• pp.98-105
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• 2021

Objective: The purpose of this study was to examined the kinematic relationship and differences through the range of motion (ROM), muscle activity, and vertical ground reaction force (VGRF) during forward and backward lunge movements, which are effective in improving muscle strength and balance ability of the lower extremities, and to provide clinical information on more efficient lunge movements. Design: Cross-sectional study Methods: Fifteen adult males who met the selection criteria were tested for their dominant feet.Forward and backward lunges were then performed, and the ROM, muscle activity, and VGRF were measured for kinematic analysis during the lunge movement.The differences betweenthe forward lunge and backward lunge intervention were examined using a paired t-test. Results: A significant increase in the ROM of the knee and ankle was observed during the forward and backward lunges (p<0.05). In addition, in terms of the muscle activity, the peak values of the vastus medialis oblique (VMO) and VGRF also showed a significant increase in the forward lunge compared to the backward lunge (p<0.05). Conclusions: This study showed an increase in VGRF peak value, knee and ankle ROM, and VMO muscle activity during forward lunge. Based on these results, it is considered necessary to apply differently depending on the direction of progress in consideration of the musculoskeletal situation and physical ability during the lunge movement.

• Food Science of Animal Resources
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• v.40 no.6
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• pp.957-968
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• 2020

The influence of muscle architecture on muscle fiber characteristics and meat quality has not been fully elucidated. In the present study, muscle fiber characteristics on the chop surface of pork loin (M. longissimus thoracis et lumborum, LTL), pennation angle degree, and meat quality were evaluated to understand the pork LTL architecture and its relationship with the loin chop quality. Muscle fiber pennation degree ranged from 51.33° to 69.00°, resulting in an ellipse-shaped muscle fiber on the surface of pork loin chop. The cross-sectional area (CSA) on the sections cut vertical to the muscle length (M-Vertical) was considerably larger (p<0.05) than that on the sections cut vertical to the muscle fiber orientation (F-Vertical) regardless of the fiber type. Pennation angle is positively correlated with CSAs of F-Vertical (p<0.05) and with Warner-Bratzler shear force (r=0.53, p<0.01). Besides the shear force, lightness and pH were positively correlated with the fiber composition and CSA of IIX fiber (p<0.05); however, the redness, yellowness, drip loss, and cooking loss were not correlated with the pennation angle and muscle fiber characteristics on the chop surface (p>0.05). These observations might help us in better understanding pork loin architecture and the relationship between the pennation angle, muscle fiber characteristics, and meat quality of pork loin chop.

• The Journal of Korea Robotics Society
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• v.5 no.1
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• pp.48-54
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• 2010

Ankle-foot orthosis with a pneumatic rubber actuator, which is intended for the assistance and the enhancement of ankle muscular activities was developed. In this study, the effectiveness of the system was investigated during plantarflexion motion of ankle joint. To find a effectiveness of the system, the subjects performed maximal voluntary isokinetic plantarflexion contraction on a Biodex-dynamometer. Plantarfexion torque of the ankle joint is assisted by subject's soleus muscle that is generated when ankle joint do plantarflexion motion. We used the muscular stiffness signal of a soleus muscle for feedback control of ankle-foot orthosis as physiological signal. For measurement of this signal, we made the muscular stiffness force sensor. We compared a muscular stiffness force of a soleus muscle between with feedback control and without it and a maximal plantarflexion torque between not wearing a ankle-foot orthosis, without feedback control wearing it and with feedback control wearing it in each ten elderly adults. The experimental result showed that a muscular stiffness force of a soleus muscle with feedback control was reduced and plantarflexion torque of an ankle joint only wearing ankle-foot orthosis was reduced but a plantarflexion torque with feedback control was increased. The amount of a increasing with feedback control is more higher than the amount of a decreasing only wearing it. Therefore, we confirmed the effectiveness of the developed ankle-foot orthosis with feedback control.

• Korean Journal of Applied Biomechanics
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• v.29 no.3
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• pp.167-172
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• 2019

Objective: The aim of this study was to investigate the effect of midsole hardness of running shoe on muscle fatigue and impact force during distance running. Method: Ten healthy college recreational runners who were performing distance running at least three times a week participated in this experiment. They were asked to run for 15 minutes in the treadmill at 10 km/h with running shoes having three different types of midsole hardness (Soft, Medium, Hard). EMG signal and insole pressure were collected during the first and last one minute for each running trials. Data were analyzed using a one-way analysis of variance (ANOVA) with repeated measures. Results: Midsole hardness did not affect the consistency of stride length. For the median frequency of the EMG signal, only VL was affected by midsole hardness; that of medium was greater than other midsoles (p<.05). The loading rate of impact forces increased by midsole hardness (p<.01). Conclusion: Although soft midsole could attenuate impact forces at heel contact, it might have a negative effect on the fatigue of muscle which could decelerate the body after heel contact. Therefore, it is necessary to select the optimum hardness of midsole carefully for both reduction impact forces and muscle fatigue.