• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.243-252
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• 2011

The purpose of this study was to determine the effect of trunk posture on muscle activity and motion of scapular and scapulohumeral rhythm. Thirty-one healthy subjects performed right-arm abduction and adduction along the frontal plane while standing in both upright and flexed posture of trunk. Scapular upward rotation, anterior tilting and internal rotation ware recorded using a motion analysis system and muscle activity of upper trapezius, lower trapezius and serratus anterior ware recorded using surface electromyography during abduction and adduction in both trunk postures. then, scapulohumeral rhythm was calculated. Scapulohumeral rhythm and scapular posterior tilting in flexed posture was significantly decreased than in upright posture. Also, muscle activity of lower trapezius in flexed posture was significantly increased and serratus anterior was significantly decreased than in general posture. The result of this study revealed that flexed posture of trunk altered the muscle activity and kinematic of scapular. Measurement of trunk posture should be included the evaluation of dysfunction and disorder of shoulder girdle since rehabilitation of trunk posture is important to restore of upper limbs function.

• PNF and Movement
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• v.20 no.2
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• pp.215-222
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• 2022

Purpose: The purpose of this study was to compare the effects of passive scapular upward rotation and posterior tilt and active scapular posterior tilt on the muscle activity of the upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA). Methods: Fifteen healthy subjects performed general arm elevation, arm elevation with passive scapular upward rotation and posterior tilt, and arm elevation with active scapular posterior tilt. For active scapular posterior tilt, the subjects were trained in this movement using visual biofeedback and a motion sensor. During each arm elevation condition, electromyography was used to measure the muscle activity of the UT, LT, and SA. The measured data were analyzed using a one-way repeated ANOVA. Results: LT muscle activity was significantly increased during arm elevation with active scapular posterior tilt compared to both general arm elevation and arm elevation with passive scapular upward rotation and posterior tilt (p < 0.05). SA muscle activity was greater during arm elevation with passive scapular upward rotation and posterior tilt than during general arm elevation (p < 0.05). There was no significant change in UT muscle activity among the tested arm elevation conditions (p > 0.05). Conclusion: Performing arm elevation with active scapular posterior tilt and performing arm elevation with passive scapular upward rotation and posterior tilt may be useful strategies for increasing muscle activation of the LT and SA, respectively.

• Journal of Convergence for Information Technology
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• v.7 no.4
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• pp.97-103
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• 2017

The purpose of this study was to investigate muscle activity of cervical erector spinae & upper trapezius while using a smartphone according to anterior pelvic tilt & posterior pelvic tilt in sitting position. & we also want to obtain basic data necessary for development of IoT devices. Fifteen healthy men & women aged 20-30 were enolled, After anterior pelvic tilt & posterior pelvic tilt in sitting position were adjusted, they used a smartphone for 5 minutes & EMG signal was measured simultaneously. We used median 3 minutes of measured EMG signal. The results of this study were as follows: In the sitting position, the use of smartphone in anterior pelvic tilt had significantly lower %RVC values in both cervical erector spinae (p <.001), left upper trapezius (p <.001) & right upper trapezius (p <.002) in comparison with posterior pelvic tilt. This means that anterior pelvic tilt make vertebrae maintain normal curvature & prevent forward head posture occurred while using a smartphone. It reduces loads around neck & shoulders, so that %RVC value is significantly lowered. In the future, new posture corrected IoT devices with an aspect of pelvic tilt should be developed.

• 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 Ergonomics Society of Korea
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• v.27 no.3
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• pp.33-41
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• 2008

The goal of this study was to compare wrist posture, muscular loads and perceived comfort among wearable wrist rest (WR), general wrist rest(GR), no wrist rest(NR) during keyboard and mouse use. Thirteen subjects performed text editing task in three test conditions: wearable wrist rest(WR), general wrist rest(GR), no wrist rest(NR). During text editing task, the right wrist posture was recorded by an electrogoniometer and the muscle activity in upper trapezius, anterior deltoid, extensor digitorum, extensor carpi ulnaris were recorded by electromyography. After all of the tests, the subjects rated perceived comfort. Working with wearable wrist rest(WR), compared to no wrist rest(NR) and general wrist rest(GR), decreased wrist radial/ulnar deviation and also decreased muscle activity in upper trapezius and anterior deltoid. At the same time, in work with wearable wrist rest(WR), the subjects rated more comfort at 5 of 8 body locations(shoulder, upper arm, wrist, hand, body).

• Journal of the Korean Society of Physical Medicine
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• v.8 no.4
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• pp.601-608
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• 2013

PURPOSE: The purpose of this study was to investigate the effect of distance between trunk and desk on forward head posture and muscle activity of neck and shoulder muscles during computer work. METHODS: Twenty subjects who have healthy conditions were asked to perform computer work in two conditions (distance between trunk and desk was 0 and 15 cm). Forward head angle was analyzed with a SIMI motion analysis system. Surface electromyography recorded the upper trapezius and splenius capitis muscles. The significance of differences in distance between trunk and desk (0cm and 15cm) was tested by paired t-test. The alpha level was set at .05. RESULTS: The results showed that the change of forward head angle was significantly higher during the computer work when the distance between trunk and desk was 15cm than 0cm. The muscle activity of upper trapezius and splenius capitis was also significantly higher during the computer work when the distance between trunk and desk was 15cm than 0cm. CONCLUSION: Our study suggest that the distance between trunk and desk was should minimized for prevention of forward head posture during computer work.

• Physical Therapy Korea
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• v.15 no.2
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• pp.38-43
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• 2008

To reduce winging scapula, various exercise protocols have been widely used by clinicians. Selective serratus anterior strengthening, and restoring balanced function, are especially recommended to reduce winging scapula. The purpose of this study was to investigate visual biofeedback using a real time video camera display system for monitoring scapular winging during arm lowering. For this study, 13 males with winging scapular were recruited during arm lowering. Electromyography (EMG) activity was recorded from the serratus anterior (SA) and upper trapezius (UT) of the right side and compared with normal EMG activity using a paired t-test. The study showed, through visual biofeedback, that EMG activity significantly increased in the SA and significantly decreased in the UT (p<.05). These results suggest that visual biofeedback can be recommended as an effective method for scapular eccentric control, to prevent scapular winging during arm lowering.

• Journal of Biomedical Engineering Research
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• v.42 no.5
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• pp.225-231
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• 2021

The purpose of this study was to investigate the effect on the activity of the upper trapezius and erector spinae according to the length difference of the backpack using electromyogram (EMG). We also conducted a study comparing the center of pressure (COP) and weight distribution before and after using Wii® balance board. Thirty individuals were randomly assigned to the experimental group (n=14) wearing a backpack with a short right strap length and a control group (n=16) wearing a backpack with the same strap length. Data were collected by dividing into groups, carring a 15% weight backpack and walking for 20 minutes on a treadmill. As a result of analyzing the EMG data, there was no significant change in the upper extremity muscle activity of the control group, but it was significantly decreased in the right upper trapezius activity of the experimental group (p<0.05). In addition, there was a significant change of COP in the experimental group (p<0.05), but there was no significant difference of the weight distribution in both groups. Recognizing mechanical changes in the body that may occur due to the asymmetry of the strap length is thought to be helpful for systematic ergonomic intervention according to changes in the external environment in the future.

• Journal of the Korean Society of Physical Medicine
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• v.8 no.3
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• pp.369-378
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• 2013

PURPOSE: The purpose of present study was to ascertain how the activity of the serratus anterior muscle, the upper trapezius muscle and the pectoral major muscle was affected while the upper arm was being flexed at 70, 90 and 110 degrees respectively in a closed kinetic chain exercise (wall push up plus) and an open kinetic chain exercise (static hug). METHODS: Sixteen healthy young men subjects participated in the study. Surface electromyography (EMG) data were collected from the dominant-side muscles during a closed kinetic chain exercise and an open kinetic chain exercise. The activity of each muscle was measured quantitatively, and by the use of the two-way repeated ANOVA, the data were compared with each other according to exercises and shoulder flexion angles. RESULTS: Results indicated that the closed kinetic chain exercise did not interact with the open kinetic chain exercise (p>.05). In both the closed kinetic chain exercise and the open kinetic chain exercise, the activity of the serratus anterior muscle became different significantly according to angles (p<.05). Its activity increased in order of 70, 90 and 110 degrees (p<.05). In both exercises and all angles, muscle activity was significantly higher in the serratus anterior muscle than in the upper trapezius muscle and the pectoral major muscle (p<.05). CONCLUSION: The above results show that there is a need to selectively control the exercise stress of the serratus anterior muscle in the case of the patients with the shoulder impingement syndrome characterized by the winged scapula, insufficient scapular protraction and upward rotation.

• Journal of the Korean Society of Physical Medicine
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• v.19 no.1
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• pp.53-60
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• 2024

PURPOSE: The study aimed to analyze the effect of pillow height on upper trapezius and sternocleidomastoid (SCM) muscle activity and overall human body comfort to determine the optimal pillow height. METHODS: The study included 32 healthy college students, of both genders, who provided prior consent. It examined three pillow heights (flat, 6cm, 12cm) and measured the upper trapezius and SCM muscles using ultrasonography, myotone, and electromyography(EMG). Muscle activation, thickness, and fatigue were assessed. RESULTS: The study found significant differences in muscle thickness and muscle tone based on the pillow heights (flat, 6cm, and 12cm) with a p < .05. The SCM and upper trapezius muscles were thinnest at a pillow height of 6cm. Muscle tone in the SCM was lower at both 6cm and 12cm pillow heights. Post-hoc measurements showed significant differences in both the SCM and upper trapezius muscles thickness at the 6cm pillow height (p < .05). Also, significant differences in muscle tone were observed only in the SCM, particularly between the 6cm and 12cm pillow heights. CONCLUSION: The ultrasonography and myotone measurements showed a significant difference in muscle thickness and muscle tension, both of which were above 6cm, while there was no difference in muscle activation. Based on the strong correlation between muscle tension and muscle thickness with pillow height, this study concluded that the human body feels comfortable with a 6cm pillow height. Therefore, it is recommended to use a pillow height of 6cm when lying in a supine position.