• Journal of the Korean Society of Physical Medicine
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• v.11 no.2
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• pp.71-76
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• 2016

PURPOSE: The purpose of this study was to compare isometric contraction of deltoid middle fiber between elastic band and light dumbbell on various shoulder abduction angle. And this study intends to examine the compare with isometric contraction on deltoid middle fiber in various abduction angle of shoulder joint. METHODS: The participants of this study were Korean healthy adult in their 20s (n=60). The 8 channel surface electromyography was used to measure activity of the deltoid middle fiber at isomeric contraction on various abduction angle: $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $90^{\circ}$, $120^{\circ}$ of shoulder joint using elastic band: red color Theraband and dumbbell: 2kg. The data used in the analysis of the present study was the root mean square. RESULTS: The deltoid middle fiber activation was not significantly different between elastic band and dumbbell at each abduction angle. The deltoid middle fiber activation significantly increased as more to increased shoulder abduction angle in elastic band and dumbbell. CONCLUSION: The elastic band and dumbbell was to provide the similarly load to the deltoid middle fiber isometric contraction on all of the shoulder abduction angle. The deltoid middle fiber activation increased as more to increased shoulder abduction angle in elastic band and dumbbell. These results may be an important reference in development of exercise on shoulder joint.

• The Journal of Korean Physical Therapy
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• v.27 no.4
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• pp.246-251
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• 2015

Purpose: The purpose of this study was to compare activities of shoulder girdle muscles according to types of closed chain exercise in the sixties. Methods: The subjects consisted of 15 persons in their sixties. Muscle activity of the pectoralis major, deltoid middle, deltoid posterior, upper trapezius, lower trapezius, and serratus anterior were measured using electromyography according to shape of the support base and angle of shoulder flexion. According to types of closed chain exercises, muscles activities were compared by paired t-test. Significance level to verify statistical significance was .05. SPSS win (ver. 22.0) program was used for statistical analysis. Results: Muscle activities of the pectoralis major, middle deltoid, trapezius lower, and serratus anterior showed significant difference according to types of closed chain exercise (p<0.05). Conclusion: According to types of closed chain exercises of the shoulder girdle, muscle activities of the pectoralis major, deltoid middle, posterior and lower trapezius showed change of muscle activities.

• Journal of the Korean Society of Physical Medicine
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• v.14 no.2
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• pp.1-7
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• 2019

PURPOSE: This study was conducted to investigate effects of shoulder adduction load on rotator cuff muscles, including the infraspinatus, during the external rotation exercise of shoulder. METHODS: This study investigated 16 healthy university students from Daegu University. Before the study started, all participants understood the content of this study. They signed an informed consent form. Five electrodes for surface electromyography (sEMG) were attached to their infraspinatus, middle deltoid, posterior deltoid, upper trapezius and pectoralis major. The participants then underwent the shoulder external rotation exercise with the shoulder adduction at three loads (0 mmHg, 20 mmHg and 40 mmHg) that were controlled using a stabilizer Pressure $Bio-feedback^{TM}$ device. The surface electrodes recorded the electromyographic data during the external rotation exercise of shoulder. RESULTS: The infraspinatus was most activated when the shoulder adduction pressure was 40 mmHg during the external rotation exercise of shoulder. The infraspinatus activation significantly increased when the shoulder adduction pressure intensity increased, while the middle deltoid activation and the posterior deltoid activation significantly decreased (p<.05). CONCLUSION: In conclusion, increases in shoulder adduction load intensity during shoulder external rotation exercises can have a positive effect on the infraspinatus, which consists of rotator cuff muscles, with minimal activity in the middle and posterior deltoid.

• The Journal of Korean Physical Therapy
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• v.34 no.5
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• pp.278-281
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• 2022

Purpose: This study sought to compare the muscle activity of the deltoid muscle according to the range of motion during the proprioceptive neuromuscular facilitation (PNF) upper extremity D2 pattern exercise performed with an isokinetic exercise device. The aim was to provide basic data for selecting an exercise for the relevant segment of the range of motion to enhance function in clinical practice. Methods: In this study, the relevant measurements of the anterior and middle trapezius of 25 healthy adults were taken using a surface electromyography system. The upper extremity pattern exercise was performed in three ranges (0% to 50%, 50% to 100%, and 25% to 75%) using the upper extremity isokinetic device. Results: There was a statistically significant difference in the muscle activity ratios of the anterior and middle deltoid muscles according to the measurement conditions (p<0.05). There was a statistically significant difference in the activity ratio of the middle deltoid muscle according to the measurement conditions in the ratio from the start range to the end range (p<0.05). There was no significant difference in the muscle onset time difference according to the measurement conditions (p>0.05). Conclusion: The muscle activity of the anterior and middle deltoid muscles was analyzed according to the range of motion during the PNF upper extremity pattern exercise performed with an isokinetic device. The results could be used as a basis for selecting exercises for the relevant segment of the range of motion according to the function to be emphasized.

• Journal of The Korean Society of Integrative Medicine
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• v.5 no.2
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• pp.19-23
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• 2017

Purpose: The purpose of this study was to determine the muscle activity ratio according to the shoulder abduction angle by identifying the mean muscle activities and calculating the muscle ratios for use in developing strengthening methods. Methods: The participants were healthy adults in their 20s (n=19). The activity of the deltoid middle, upper trapezius, middle trapezius, and lower trapezius muscles was measured by 8-channel surface electromyography. Muscle activity was measured during 4 conditions of angle of shoulder abduction: $30^{\circ}$, $60^{\circ}$, $90^{\circ}$, and $120^{\circ}$. The data used in the analysis were the root mean square and % total muscle activity values. Results: The root mean square values for the deltoid middle, upper trapezius, middle trapezius, and lower trapezius muscles showed significant differences. No significant differences were detected in the % total muscle activity of the deltoid middle, upper trapezius, middle trapezius, or lower trapezius muscles. Conclusion: Future studies aimed at developing selective shoulder abductor muscle strengthening methods are likely to provide more effective results by using muscle activity ratios.

• Physical Therapy Korea
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• v.15 no.2
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• pp.73-80
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• 2008

With the introduction of the video display terminal (VDT), the efficiency and productivity of work has improved. However, VDT syndrome is threatening the health of workers as a side effect of prolonged use of a VDT. Among various VDT syndromes, the musculoskeletal disorder, especially, the cumulative trauma disorder (CTD) is the common research topic related with upper extremities function. The aim of this study was to investigate the effect of the wrist-hand orthosis (WHO) on fatigue in middle deltoid, anterior deltoid, serratus anterior, and upper trapezius during one-hour computer keyboard typing. Twelve healthy subjects participated in this study. Surface electromyography was used to assess the localized muscle fatigue (LMF), and the LMF was calculated at 10 minutes, 20 minutes, 40 minutes, and 60 minutes in each muscle, with and without the WHO. Data were analyzed by paired t-test with a level of significance of .05. The results of this study are as follows: 1) At 10 minutes, the LMF decreased significantly with applied WHO in the middle deltoid, anterior deltoid, and upper trapezius (p=.001, p=.026, p=.019, respectively). 2) As the computer keyboard typing period increased, there were no significant LMF differences, except for the upper trapezius. Therefore, it can be concluded that the WHO can be applied to decrease the LMF for the initial 10 minute period in the middle deltoid, anterior deltoid, and upper trapezius' but that the long term effect of WHO in reducing the LMF was proven only in upper trapezius during continued computer keyboard typing.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.3
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• pp.101-108
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• 2015

PURPOSE: This study researched the effects of the changes of elbow joint angle and of arm position in PNF pattern on muscle activation of the contralateral shoulder muscles while performing PNF pattern exercise. METHODS: The research subjects were 16 male physical therapists who had no neuromuscular or neurological disorders. To measure the muscle activation of the contralateral shoulder muscles, EMG electrodes were attached to the muscle valley of the middle and posterior areas of the deltoid and triceps muscles of the arm. Muscle activation while performing the ulnar thrust PNF pattern exercise was measured with the elbow joint positioned at angles of $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$. Resistance points were at the initial, middle, and end ranges of PNF pattern exercise. RESULTS: Muscle activation of the middle and posterior portions of the deltoid muscle increased significantly according to the changes of elbow joint angle. In each resistance point the middle range was significantly higher than at other points. A significant difference on muscle activation was demonstrated throughout each range depending on the type of muscle. Muscle activation of the middle and posterior portions of the deltoid muscle was higher than muscle activation of the triceps. CONCLUSION: The results of this study demonstrate that the PNF pattern exercising method used in this study is a selective exercising method focusing on the deltoid muscle over the triceps muscle. In order to increase the muscle strength to the maximum level, it is necessary to provide the maximum level of resistance in the middle range of the elbow joint.

• Journal of Biomedical Engineering Research
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• v.38 no.2
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• pp.74-81
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• 2017

The purpose of this study was to investigate the EMG characteristics of driver's upper extremity and driving performance for manipulating brake and accelerator pedal by using left and right hand control devices during simulated driving. The people with disabilities in the lower limb have problems in operation of the motor vehicle because of functional loss for manipulating brake and accelerator pedal. Therefore, if hand control device is used for adaptive driving controls in people with lower limb impairments, the disabled people can improve their quality of life by driving a motor vehicle. Six subjects were participated in this study to evaluate driving performance and muscle activities for operating brake and accelerator pedal by using two different hand controls (steering column mounted hand control and floor mounted hand control) in driving simulator. We measured EMG activities of six muscles (posterior deltoid, middle deltoid, triceps, biceps, flexor carpi radialis, and extensor carpi radialis) during pushing and pulling movement with different hand controls for acceleration and braking. STISim Drive 3 software was used for the performance test of different hand control devices in straight lane course for time to reach target speed and brake reaction time. While pulling the hand control lever toward the driver, normalized EMG activities of middle deltoid, triceps and flexor carpi radialis in subjects with disabilities were significantly increased (p < 0.05) compared to the normal subjects. It was also found that muscle responses of posterior deltoid were significantly increased (p < 0.05) when using the right hand control than left hand control. While pushing the hand control lever forward away from the driver, normalized EMG activities of posterior deltoid, middle deltoid and extensor carpi radialis in subjects with disability were significantly increased (p < 0.05) compared to the normal subjects. It was shown that muscle responses of middle deltoid, biceps and extensor carpi radialis were significantly increased when using the right hand control than left hand control. Brake reaction time and time to reach target speed in subjects with disability was increased by 12% and 11.3% on average compared to normal subjects. The subjects with physical disabilities showed a tendency to relatively slow acceleration at the straight lane course.

• The Journal of Korean Physical Therapy
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• v.24 no.6
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• pp.388-392
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• 2012

Purpose: Muscle imbalance between upper trapezius (UT) and serratus anterior (SA) during arm elevation is a factor causing shoulder dysfunction. However, there is no study to compare the muscle activities of the UT and middle deltoid (MD). The purpose of this study was to compare the muscle activities of the UT and MD between with and without elevation of shoulder girdle (ESG) during shoulder abduction. Methods: The subjects without (control group=9) or with (ESG group=8) participated in this study. The muscle activities of the UT and MD were measured using a electromyography during $90^{\circ}$ shoulder abducted position in both group. The data in middle of 3-second of the 5-second periods were used. The mean value of three trials was used in the data analysis. For each muscle, independent t-tests were performed to compare for group differences. Results: The muscle activity of UT was significantly greater in ESG group, compared to that of the control group (p<0.05). The muscle activity of MD was significantly smaller in ESG group, compared to that of the control group (p<0.05). Conclusion: These findings showed that low muscle activation of MD as well as SA may contribute to hyperactivity of UT during arm elevation.

• Journal of the Ergonomics Society of Korea
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• v.31 no.2
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• pp.281-289
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• 2012

Objective: The purpose of this study is to evaluate the potential risk of shoulder muscle at particular working postures in sitting. Background: The cause of shoulder pain needs to be specifically studied in relation with particular shoulder postures to prevent shoulder MSDs in workplace. Method: In this study MVC, fatigue and subjective workload were investigated depending on the change of shoulder posture. An experiment was designed to evaluate the six shoulder muscles at nine shoulder postures including the combination of 30(adduction), 0, 30(abduction) degrees and 60, 90, and 120 degrees of shoulder flexion. Surface electrodes were attached to the middle trapezius, inferior middle trapezius, anterior deltoid, posterior deltoid, serratus anterior and teres major. Thirteen subjects participated in the experiment. Dependent variables were RPE (rating of perceived exertion), MVC(maximum voluntary contraction) and MPF(mean power frequency) shift by EMG (electromyography). Results: The middle trapezius and inferior middle trapezius were not significantly fatigued at all postures. The decline of MPF slope was less than 10% at all postures. The anterior deltoid was significantly fatigued all postures. The decline of MPF slope was more than 10% at all postures. The posterior deltoid was significantly fatigued 30 degrees of adduction and 90 degrees of flexion. And, neutral and 30 degrees of abduction postures were fatigued more than 90 degrees of flexion. The serratus anterior was significantly fatigued except for 30 degrees of adduction and 60 degrees of flexion posture. The teres major was significantly fatigued except for neutral and 60 degrees of flexion, 30 degrees of abduction and 60 degrees of flexion posture. Conclusion: It was found that a certain muscle was fatigued fast at particular posture compared to other muscles, which would mean that a certain shoulder muscle at particular posture could be easily exposed to the risk of musculoskeletal disorders than other muscles. Application: It is expected that the result can be applied to design workplace using shoulder muscles.