• PNF and Movement
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• v.13 no.1
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• pp.1-7
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• 2015

Purpose: This study aimed to examine the activity of the shoulder flexor and extensor when hold-relax and contraction-relax techniques were applied with shoulder joint flexion. Methods: The subjects of this study were 15 healthy women. With the shoulder joint flexion at $0^{\circ}$ and $90^{\circ}$, hold-relax and contraction-relax techniques were applied for the same submaximal resistance to measure the activities of the deltoid muscle anterior fiber, deltoid muscle posterior fiber, pectoralis major fiber, and latissimus dorsi muscle with surface electromyography. An independent t-test was conducted in order to compare activities of each muscle according to the two techniques. Results: When the hold-relax and contraction-relax techniques were applied with the shoulder joint flexion at $0^{\circ}$, the activities of the shoulder flexor and extensor were not significantly different, but the activity of the flexor was higher when the contraction-relax technique was applied than when the hold-relax technique was applied. When the hold-relax and contraction-relax techniques were applied with the shoulder joint flexed at $90^{\circ}$, the activities of the shoulder flexor and extensor were not significantly different, but the activity of the extensor was relatively higher than when the flexor was at $0^{\circ}$ Conclusion: When the hold-relax and contraction-relax techniques were applied with the shoulder joint flexion at $0^{\circ}$, the activities of the shoulder flexor and extensor were not significantly different, but the activity of the flexor was higher when the contraction-relax technique was applied than when the hold-relax technique was applied. When the hold-relax and contraction-relax techniques were applied with the shoulder joint flexed at $90^{\circ}$, the activities of the shoulder flexor and extensor were not significantly different, but the activity of the extensor was relatively higher than when the flexor was at $0^{\circ}$.

• Korean Journal of Applied Biomechanics
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• v.32 no.4
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• pp.128-133
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• 2022

Objective: This study was executed to compare and analyze shoulder muscle activation while using an inelastic bar and elastic bar during overhead press exercise. The stability and coordination of shoulder joints will be investigated by measuring and analyzing the EMG of the upper and lower arm muscles. Method: A total of 20 university male students were recruited by dividing into 2 groups; 10 elastic bar participants (age: 20.17 ± 0.41 yrs, height: 174.31 ± 3.34 cm, weight: 74.68 ± 5.65 kg) and 10 inelastic bar participants (age: 20.09 ± 0.23 yrs, height: 173.53 ± 4.11 cm, weight: 75.32 ± 3.31 kg) participated in this study. Results: The EMG analysis results of the four muscles measured in this study showed that there was no difference between the left and right muscles between the groups in Upper Trapezius muscle. In Deltoid, Infraspinatus, and Rectus Abdominis muscles, the elastic bar group was significantly higher than the inelastic bar group between groups, and there was no difference between left and right. Conclusion: Among the four muscles measured in this study, there was no difference between left and right in Deltoid, Infraspinatus, and Rectus Abdominis, but the elastic bar showed significantly higher muscle activity than the inelastic bar. Therefore, it was found that the elastic bar increases muscle activation during exercise than the inelastic bar, and in particular, it further increases muscle activation of the arms and torso, and exercise using the elastic bar can increase neuromuscular stabilization.

• Physical Therapy Korea
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• v.25 no.1
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• pp.62-70
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• 2018

Background: Sitting posture influences movements of scapulothoracic and glenohumeral joints and changes the shoulder muscle activities. The development and maintenance of correct sitting posture is important for the fundamental treatment of shoulder pain during rehabilitation. Objects: The purpose of this study was to investigate the effects of the sitting postures and the shoulder movements on shoulder muscle activities for both male and female. Methods: Twenty-eight subjects without shoulder-related diseases participated in this experiment. The subjects had randomly adopted three different sitting postures (upright posture, preferred posture, maximum slouched posture) and shoulder flexion angles in scapular plane ($30^{\circ}$, $90^{\circ}$, $120^{\circ}$). Surface electrodes were collected from upper trapezius (UT), anterior deltoid (AD), and posterior deltoid (PD) and the active shoulder range of motion was measured in each sitting posture and shoulder flexion angle. Results: The active range of motions of the shoulder external rotation and the flexion in the scapular plane decreased from the upright posture to the maximum slouched posture (p<.05, mixed-effect linear regression with random intercept, Tukey post-hoc analysis). All muscles showed the highest EMG activities at $120^{\circ}$ shoulder flexion with the maximum slouched posture and did not show the gender differences. Conclusion: Increased shoulder muscle activities may become the potential risk factor for the shoulder impairment and pain if people continuously maintain the maximum slouched posture. Therefore, an upright position is necessary during shoulder exercises, as well as in activities of daily living, including motions involving lifting the arms.

• The Journal of Korean Medicine
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• v.39 no.4
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• pp.121-125
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• 2018

Objectives: This study was carried out to analyse Hand Greater Yang Skin in human. Methods: Hand Greater Yang meridian was labeled with latex in the body surface of the cadaver. And subsequently body among superficial fascia and muscular layer were dissected in order to observe internal structures. Results : A depth of Skin encompasses a common integument and a immediately below superficial fascia, this study established Skin boundary with adjacent structures such as relative muscle, tendon as compass. The Skin area of the Hand Greater Yang in human are as follows: The skin close to 0.1chon ulnad of $5^{th}$ nail angle, ulnad base of $5^{th}$ phalanx, ulnad head of $5^{th}$ metacapus(relevant muscle: abductor digiti minimi muscle), ulnad of hamate, tip of ulnar styloid process(extensor carpi ulnaris tendon), radiad of ulnar styloid process, 2cm below midpoint between Sohae and Yanggok(extensor carpi ulnaris), between medial epicondyle of humerus and olecranon of ulnar(ulnar nerve), The skin close to deltoid muscle, trapezius muscle, platysma muscle, inner muscles such as teres major muscle, infraspinatus muscle, supraspinatus muscle, levator scapulae muscle, splenius cervicis muscle, splenius capitis muscle, sternocleidomastoid muscle, digastric muscle, stylohyoid muscle, zygomaticus major muscle, auricularis anterior muscle. Conclusions: The Skin area of the Hand Greater Yang from the anatomical viewpoint seems to be the skin area outside the superficial fascia or muscles involved in the pathway of Hand Greater Yang meridian, collateral meridian, meridian muscle, with the condition that we consider adjacent skins.

• Journal of Digital Convergence
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• v.10 no.9
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• pp.435-441
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• 2012

This study is intended to provide a basic clinical data useful for preventing shoulder injuries related to occupation and curing them, by measuring the shoulder muscle activity of normal adults in an arm posture type of a wide shoulder joint angle, according to several differences of hand grip force. In order to examine the shoulder muscle activity during hand grips at a variety of intensity, according to the arm posture type, MVCs of all subjects were measured, and %MVCs of anterior deltoid, supraspinatus, the upper trapezius and infraspinatus at 0 degree, 90 degrees and 160 degrees of shoulder angle were yielded according to the grip force in an arm posture type, changing the maximum grip force into 30%, 50% and 90%, randomly. When measuring the hand grip at 30%, 50% and 70% of the maximum grip force to compare %MVC of each group depending on the arm posture type, there were no significant differences of muscle activity at 0 degree of shoulder angle among anterior deltoid, supraspinatus, the upper trapezius and infraspinatus, but there were significant differences of it among them at 90 degrees and 160 degrees of should angle(p<.001). According to the results of post-hoc test, also, anterior deltoid had the highest muscle activity, whereas the upper trapezius had the lowest muscle activity.

• Journal of the Korea Safety Management & Science
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• v.11 no.3
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• pp.79-85
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• 2009

In this study, the effects of psychosocial stress (box color and precision demand) on muscle activity were evaluated in laboratory setting. Eight subjects performed sagittally symmetric lifting tasks. Box color (yellow, black), precision demand (yes, no), and box weight (5%MVC, 10%MVC, 15 %MVC) were varied and surface EMG signals from seven muscles(medial deltoid right, biceps brachii right, lateral triceps right, latissimus dorsi right, erector spinae right, external oblique right, internal oblique right) were recorded. EMG signals were band-pass filtered($10{\sim}400\;Hz$), rectified, RMS smoothed and normalized (NEMG). Analysis of variance tests were conducted on the total NEMG (TNEMG: the sum of the seven muscles' NEMGs) and on the individual muscle's NEMGs. Box color had no effect on the TNEMG and on the seven muscles activities(p>0.05). When precision demand was required at the end point of lifts, the mean NEMG showed higher values than no precision demand conditions: TNEMG (14% increase) and medial deltoid(40% increase), biceps brachii(10% increase), lateral triceps(26% increase), latissimus dorsi(25% increase) muscles. Those increases showed more conspicuous as the box weight increased in the muscles of medial deltoid, lateral triceps, and latissimus dorsi.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2009.03a
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• pp.74-74
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• 2009

The purpose of this study was to estimate force of muscles that constituted the rotator cuff during elevation motion in scapula plane, using a skeletal muscle model and quantitatively evaluate rotator cuff function in vivo. A healthy volunteer was measured with an open MR and CT system at elevation positions in scapula plane (MR: $30^{\circ}$, $60^{\circ}$, $90^{\circ}$, $120^{\circ}$, $150^{\circ}$, CT: $0^{\circ}$). After reconstruction three-dimensional MRI-based and CT-based bone surface models, matched each models with registration technique. Then supraspinatus, infraspinatus, subscapularis, teres minor, deltoid (anterior, middle, posterior portions) represented as plural lines. These lines were proportional to physiologic cross-sectional area (PCSA) and defined straight line to bind origin and insertion. Force of supraspinatus became greatest at $59^{\circ}$ of elevation. Subsequently force of deltoid middle portion became greatest at $89^{\circ}$ of elevation. Infraspinatus and subscapularis were active at the meantime. In addition, supraspinatus was active during elevation. These results resembled clinical finding and were proved force couples that contribute to mobility and stability of shoulder complex.

• Clinics in Shoulder and Elbow
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• v.23 no.2
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• pp.100-104
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• 2020

Function and strength of the deltoid muscle are important in reverse shoulder arthroplasty (RSA). Moreover, location and shape of the acromion, clavicle, and scapular spine, which are origins of the deltoid muscle, are also important. The frequency of os acromiale is 5% to 15%; however, it is rare in the Asian population, affecting approximately 0.7% of Koreans. RSA has rarely been reported in patients with os acromiale. We present a case series of two patients with cuff tear and arthropathy combined with os acromiale who underwent RSA. From 2016 to 2018, two patients with os acromiale who presented with pain and limited range of motion (ROM) underwent RSA with cuff tear arthropathy using the subscapularis-sparing deltopectoral approach. Their ROM, visual analog scale (VAS), and satisfaction were evaluated before and after surgery. In both patients, VAS decreased, ROM increased, and postoperative satisfaction increased. There were no specific complications due to os acromiale. The VAS, ROM, and satisfaction of patients improved after surgery compared with values before surgery. However, careful attention must be given during surgery to ensure optimal repair and recovery.

• 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).

• Physical Therapy Rehabilitation Science
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• v.11 no.2
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• pp.145-153
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• 2022

Objective: The purpose of this study was to evaluate the Electromyography (EMG) of the upper limb during reaching tasks according to two heights in the sitting position. Design: Cross sectional design Methods: Fifteen hemiplegia, fifteen elderly, and fifteen healthy subjects have participated in this study. The targets (90% length of the subject's arm) were located at the two heights (the eye and xiphoid process). We have recorded EMG signals of seven upper limb muscles (anterior deltoid (AD), posterior deltoid (PD), pectoralis major (Pec), infraspinatus (Inf), supraspinatus (Sup), biceps brachii (Bi), triceps brachii (Tri)). The dependent variables were movement time(s), modulation ratio, working ratio, and the co-contraction ratio of the hemiplegia, elderly, and healthy at the reaching task. Two-way repeated-measures ANOVA (2-heights) was analyzed with the LSD post hoc test. Results: The study results were as follows: (1) The movement time to the target during reaching movement was significantly longer for the hemiplegia and elderly groups compared to the healthy group. (2) The modulation rate was significantly higher at eye height than the xiphoid height in AD, PD, Pec, Inf, Bi muscles, and the hemiplegia group and elderly group were significantly lower than the healthy group. Additionally, the modulation ratio showed a significant interaction between heights and groups. Conclusions: It is expected that the variables using the muscle contraction characteristics, the evaluation method of this study, can be used as an electromyography-based feedback method that can be objectively evaluated and quantified in clinical practice.