• 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.

• Physical Therapy Korea
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• v.19 no.1
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• pp.46-55
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• 2012

The purpose of this study was to investigate the effect of the two different types of chairs on trapezius muscle activation during dictation tasks. Seventeen university students, each of whom were within ${\pm}1$ standard deviation of the mean Korean standard body size, voluntarily participated in this study. Surface electromyography was used to collect electrical signals from both the upper and lower trapezius muscles. Amplitude Probability Distribution Function (APDF) was performed to analyze the muscle activity. The findings of this study were 1) The backrest-point height of the auditorium chair and the height, length and width of the connected desk were shorter than what was suggested by the KS. Another difference was that the auditorium chair had a bigger angle of the backrest compared to the classroom chair. 2) Regarding within-subject effect the sole statistically significant difference was found between activation of the upper trapezius muscle. The upper trapezius muscle's %RVC in the APDF 10th-50th-90th percentile was statistically higher for participants sitting in the auditorium chair than for participants sitting in the classroom chair (p<.05). 3) There was an interaction effect between the 'two chair-types' and the 'two muscle-sides' in the APDF 10th-50th percentile (p<.05). 4) There was an interaction effect between the 'two chair-types' and the 'three gaze-direction' in the APDF 90th percentile (p<.05). The findings of this study indicated that maintaining a writing posture for a prolonged period of time in an auditorium chair significantly increased the left upper trapezius muscle activation compared to a classroom chair.

• Molecules and Cells
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• v.20 no.2
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• pp.263-270
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• 2005

Transactivation of EGF-receptor (EGFR) by G-protein coupled receptors (GPCRs) is emerging as an important pathway in cell proliferation, which plays a crucial role in the development of atherosclerotic lesion. Angiotensin II (Ang II) has been identified to have a major role in the formation of atherosclerotic lesions, although the underlying mechanisms remain largely unclear. We hypothesize that Ang II promotes the proliferation and migration of smooth muscle cells through the release of heparin-binding epidermal growth factor like growth factor (HB-EGF), transactivation of EGFR and activation of Akt and Erk 1/2, with matrix metalloproteases (MMPs) playing a dispensable role. Primary rat aortic smooth muscle cells were used in this study. Smooth muscle cells rendered quiescent by serum deprivation for 12 h were treated with Ang II (100 nM) in the presence of either GM6001 ($20{\mu}M$), a specific inhibitor of MMPs or AG1478 ($10{\mu}M$), an inhibitor of EGFR. The levels of phosphorylation of EGFR, Akt and Erk 1/2 were assessed in the cell lysates. Inhibition of MMPs by GM6001 significantly attenuated Ang II-stimulated phosphorylation of EGFR, suggesting that MMPs may be involved in the transactivation of EGFR by Ang II receptor. Furthermore Ang II-stimulated proliferation and migration of smooth muscle cells were significantly blunted by inhibiting MMPs and EGFR and applying HB-EGF neutralization antibody, indicating that MMPs, HB-EGF and EGFR activation is necessary for Ang-II stimulated migration and proliferation of smooth muscle cells. Our results suggest that inhibition of MMPs may represent one of the strategies to counter the mitogenic and motogenic effects of Ang II on smooth muscle cells and thereby prevent the formation and development of atherosclerotic lesions.

• Physical Therapy Rehabilitation Science
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• v.6 no.1
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• pp.39-44
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• 2017

Objective: The purpose of this study is to show the effectiveness of performing squat exercises at various angles to show the maximum muscle activity of the Vastus Medialis Oblique (VMO) and Biceps femoris (BF). Design: Cross-sectional study. Methods: A total of seventeen healthy young adults (8 males and 9 females) voluntarily participated in the study. All subjects randomly performed three different squat variations as follows: A squat performed with the ankle joint at $0^{\circ}$ of incline, a squat performed with the ankle joint at $5^{\circ}$ of incline, and a squat performed with the ankle joint at $10^{\circ}$ incline. Muscle activity was measured using surface electromyography. Electrodes were placed on the VMO and BF to measure the muscle activity on the various ankle angles for comparison analysis. Results: There was a significant increase in bilateral VMO muscle activation at $10^{\circ}$ of incline compared to $0^{\circ}$ and $5^{\circ}$ (p<0.05). Greater increases in muscle activation and exercise effect was observed with increasing incline angles of the board. Changes in bilateral BF muscle activity were found; however, none were found to be significant. Conclusions: Bilateral VMO activity was found to be significant when the squats were performed at an ankle angle of $10^{\circ}$ of incline when compared to at an ankle angle of $0^{\circ}$ and $5^{\circ}$ of incline. Squats performed on an incline can be recommended as an effective method to facilitate lower extremity muscle activities.

• Molecules and Cells
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• v.27 no.2
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• pp.167-173
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• 2009

The classical type of transient receptor potential (TRPC) channel is a molecular candidate for $Ca^{2+}$-permeable cation channels in mammalian cells. Because TRPC4 and TRPC5 belong to the same subfamily of TRPC, they have been assumed to have the same physiological properties. However, we found that TRPC4 had its own functional characteristics different from those of TRPC5. TRPC4 channels had no constitutive activity and were activated by muscarinic stimulation only when a muscarinic receptor was co-expressed with TRPC4 in human embryonic kidney (HEK) cells. Endogenous muscarinic receptor appeared not to interact with TRPC4. TPRC4 activation by $GTP{\gamma}S$ was not desensitized. TPRC4 activation by $GTP{\gamma}S$ was not inhibited by either Rho kinase inhibitor or MLCK inhibitor. TRPC4 was sensitive to external pH with $pK_a$ of 7.3. Finally, TPRC4 activation by $GTP{\gamma}S$ was inhibited by the calmodulin inhibitor W-7. We conclude that TRPC4 and TRPC5 have different properties and their own physiological roles.

• The Journal of Korean Physical Therapy
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• v.25 no.6
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• pp.393-398
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• 2013

Purpose: The purpose of this study was to compare muscle activation patterns of lower extremities in stroke patients during stepper climbing, stair-up, and level-ground gait conditions by surface electromyography (EMG). Methods: Subjects included 19 hemiplegic patients comprehensive rehabilitation center for inpatients with stroke. Surface EMG was used to measure the subjects' medial gastrocnemius (GCM), tibialis anterior (TA), biceps femoris (BF), and rectus femoris (RF) activity as they took six steps during stepper climbing, stair-up, and level-ground gait conditions. Results: There was no significant difference in the BF or RF muscle activity for the stepper climbing, stair-up, and level-ground gait conditions. However, there were significant differences in the medial GCM and TA muscle activity between each condition on the patients' hemiplegic side(p<0.05). There was significant difference in the medial GCM, TA, RF, and BF muscle activity between each condition on the patients' non-hemiplegic side (p<0.05). Conclusion: As a result, the overall muscle activity during the level-ground gait was higher than the stair-up condition, and the muscle activity during the stair-up condition was higher than the muscle activity during the stepper climbing condition. As one of the many methods used for gait training, we suggest that the stepper exercise could be applied at an earlier stage in the gait training process.

• Journal of Society of Preventive Korean Medicine
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• v.12 no.3
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• pp.115-128
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• 2008

Purpose : This study was performed to distinguish the muscle activation of vastus medialis and biceps femoris through open and closed kinetic chain exercise. Methods : 31 healthy male and female students in Daegu Health College were participated in this study. All subjects were conducted three types open and closed kinetic chain exercises to examine muscle activity during the last four seconds using the sEMG system. Collected EMG data were normalized using the maximal voluntary isometric contraction(MVIC). Results : MVIC of each muscle was showed significantly increased(p<0.5). In the case of open chain exercise, the type 3 exercise most increased than type 2 and 3 exercise in vastus medialis than biceps femoris muscle. The closed chain exercise presented type 6 exercise most increased than type 4 and 5 exercise in biceps femoris than vastus medialis. Conclusion : This study finally proved that muscle activity which maintains stability of knee differ from depending on the types of exercises. Therefore, the combination of the two chain exercises is believed to greatly contribute to increments in muscle activity.

• Journal of Digital Convergence
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• v.18 no.2
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• pp.483-487
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• 2020

In this study, the effects of suspension training according to the types of ground. Fourteen healthy male college students measured for the characteristics of core muscle activity in suspension training on two different types of grounds, normal flat and unstable ground using a gym ball. EMG (Electromyography) was exploited to measure the activity of the core muscles according to the types of the ground. Muscle activity of the abdominal muscles, external oblique muscles, internal oblique muscles, and lower lumbar standing muscles was measured. The variables in analyses were measured by the means of % MVC method to standardize the EMG signal according to the ground type for each core muscle. In order to verify the differences in core muscles according to the type of ground the paired t-tests were performed at the significance level of 0.05 (p<.05). As a result of measuring the activity of the core muscles according to the various types of grounds, the difference between muscle characteristics obtained in two different grounds did not appear to be statistically significant. However, the result is an important clue to reconsider the notion that the training effect on the unstable ground is generally superior to the effect on the stable ground in the core muscle training. The type of ground in the core muscle training has been found not to significantly affect the muscle activation according to the results of this study. Regardless of the type of exercise program, hence, the difference in muscle activation will not be insignificant even with the standardized program strengthening core muscles.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.352-355
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• 1998

A musculotendon model is investigated to show muscle fatigue under the repeated functional electrical stimulation (FES). The normalized Hill-type model can predict the decline in muscle force. It consists of nonlinear activation and contraction dynamics including physiological concepts of muscle fatigue. A muscle fatigue as a function of the intracellular acidification, pHi is inserted into contraction dynamics to estimate the force decline. The computer simulation shows that muscle force declines in stimulation time and the change in the estimate of the optimal fiber length has an effect only on muscle time constant not on the steady-state tetanic force.

• Physical Therapy Korea
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• v.19 no.2
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• pp.29-38
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• 2012

This study aimed to identify the asymmetry observed in the electromyography (EMG) activity patterns of selected trunk and thigh muscles between the affected and unaffected sides during the sit-to-stand movement in ambulatory patients with post-stroke hemiparesis. This study included 20 patients with post-stroke hemiparesis. The differences between stroke fast walkers (${\geq}8m/s$, 11 subjects) and stroke slow walkers (<8 m/s, 9 subjects) were compared. The activation magnitude and onset time of the multifidus, lumbar erector spinae, hamstrings, and quadriceps during the sit-to-stand movement were recorded through surface EMG. Moreover, the EMG activation magnitude and onset time ratios of each bilateral corresponding muscle from the trunk and leg were measured by dividing the relevant values of the unaffected side by those of the affected side. In all the subjects, the activation magnitudes of the multifidus, hamstring, and quadriceps on the affected side significantly decreased compared to those on the unaffected side (p<.05). The onset time of muscle activity in the affected side was markedly delayed for the multifidus and quadriceps during the task (p<.05). The activation magnitude ratios of the quadriceps were markedly decreased in the stroke slow walkers as compared to those in the stroke fast walkers. These findings indicate that the asymmetry in the multifidus, hamstring, and quadriceps muscle activation patterns in patients with post-stroke hemiparesis may be due to the excessive muscle activation in the unaffected side to compensate for the weakened muscle activity in the affected side. Our findings may provide researchers and clinicians with information that can be useful in rehabilitation therapy.