Background: Individuals with scapular winging have a weak serratus anterior (SA) muscle, and to compensate, the pectoralis major (PM) and upper trapezius (UT) muscles excessively activate, which can cause upper extremity dysfunction. This study aimed to compare the effects of isometric horizontal abduction (IHA) on SA, PM, and UT muscle activity, as well as the SA/PM and SA/UT muscle activity ratios during knee push-up plus (KPP) at 90° and 120° of shoulder flexion. Objects: This study aimed to compare the effects of IHA on SA, PM, and UT muscle activity, as well as the SA/PM and SA/UT muscle activity ratios during KPP at 90° and 120° of shoulder flexion. Methods: This study, conducted at a university research laboratory, included 20 individuals with scapular winging. Participants performed KPP with and without IHA at 90° (KPP90) and 120° (KPP120) of shoulder flexion. SA, PM, and UT muscle activity were measured using surface electromyography. Results: PM activity in KPP90 with IHA was significantly lower than KPP90 and in KPP120 was significantly lower than KPP90. UT activity was significantly greater with IHA than without IHA and at 120° than 90° of shoulder flexion. SA/PM muscle activity ratio was significantly higher in KPP90 with IHA than without IHA and in KPP120 than in KPP90. SA/UT muscle activity ratio was significantly lower with IHA than without IHA. Conclusion: KPP90 with IHA and KPP120 are effective exercises to reduce PM activity and increase SA/PM muscle activity ratio. However, applying IHA in KPP90 also reduces SA/UT muscle activity ratio, implying that it would be preferable to apply KPP120 in individuals overusing their UT muscles.

Background: Scapular dyskinesis may cause not only rotator cuff (RC) tear but also weakness of the upper extremity, studies on scapular dyskinesis that may occur after RC repair is still lacking. Objects: To determine whether scapular dsykinesis was present in patients after arthroscopic RC repair and to investigate the influence of passive scapular stabilization on upper extremity strength. Methods: A total of 30 patients after RC repair participated in this study. To compare the scapula of the arthroscopic RC repair shoulder and the contralateral shoulder, the winged scapula (WS) was measured using a scapulometer and scapular dyskinesis was also classified by type. Fixed instruments for muscle strength measurements were used to measure upper extremity muscle strength differences depending on passive scapular stabilization position or natural scapular position. A chi-square test, an independent t-test and a 2-way mixed measures analysis of variance (ANOVA) was used as statistical analysis. In analyses, p < 0.05 was deemed to be statistically significant. Results: Postoperative shoulder had a significant association with scapular dyskinesis and the WS compared to the contralateral shoulder (F = 0.052, p < 0.01). Postoperative shoulder, muscle strength in the shoulder abduction (p < 0.01), elbow flexion (p < 0.01) and forearm supination (p < 0.05) were significantly greater in the scapular stabilization position than in the scapular natural position. Conclusion: Patients underwent arthroscopic RC repair had a significant association with scapular dyskinesis and muscle strength was improved by a passive scapular stabilization position, therefore scapular stabilization is important in rehabilitation program.

Background: Individuals with scapular winging may have proprioceptive dysfunction which is important for motor control and causes shoulder instability. Reduced serratus anterior (SA) and lower trapezius (LT) muscle activity accompanied by over-active upper trapezius (UT), and pectoralis major (PM) may be contributing factors. Flexi-bar (FB) exercise may be used to increase joint position sense (JPS) and alter the target muscle activities. Objects: This study aimed to investigate the immediate effects of flexi-bar exercise prior to knee push-up plus (FPK) versus knee push-up plus (KPP) on JPS and muscle activity of SA, LT, UT, and PM in subjects with scapular winging. Methods: Eighteen subjects with scapular winging were recruited. JPS was investigated at baseline, after KPP and after FPK. Passive and active JPS errors were calculated by isokinetic equipment. Surface electromyography was used to record muscle activities during KPP and FPK. One-way repeated-measures analysis of variance and post hoc analyses were used to analyze the JPS error measured at baseline, after KPP and after FPK. Paired t-tests were used to compare muscle activities between KPP and FPK. Results: Passive JPS error was significantly decreased after KPP (p = 0.005) and after FPK (p = 0.003) compared to the baseline. Active JPS error was also significantly decreased after KPP (p = 0.016) and after FPK (p = 0.012) compared to the baseline. There was no significant difference in the passive and active JPS errors between KPP and FPK. SA activity during FPK was significantly increased (p = 0.024), and LT activity during FPK was significantly increased (p = 0.006). There were no significant differences in the UT and PM activity. Conclusion: FB might be recommended to immediately improve passive and active JPS and to selectively increase SA and LT muscle activities during KPP in individuals with scapular winging.

Background: The scapulo-thoracic musculatures including serratus anterior (SA), upper trapezius and lower trapezius can provide shoulder stability and functional shoulder movement. Objects: The muscle activities of upper and lower SA were compared during three different scapular protraction exercises in healthy individuals in sitting position. Methods: Twenty-five healthy subjects were participated. Electromyography device was used to measure muscle activity of upper and lower SA and trapezius muscles. Each subject was asked to perform three different scapular protraction exercises (scapular protraction [SP], SP with self-resistance [SPSR], SPSR with hand-exerciser [SPSRH]) in random order. One-way repeated measures analysis of the variance and a Bonferroni post hoc test were used. Results: The muscle activity of lower SA muscle was significantly different among three conditions (SP vs. SPSR vs. SPSRH) (p < 0.01). The lower SA muscle activity was significantly greater during SPSRH compared to SP and SPSR, which required joint stability more than SP and SPSR (p < 0.01). Conclusion: SPSRH exercise can be recommended to facilitate the muscle activity of lower SA. In addition, the intramuscular variation in the upper and lower SA during scapular protraction exercise is required to consider the effective rehabilitation.

Background: Although the scapular posterior tilt movement could facilitate the lower trapezius (LT) muscle activity, no study identified the effects of the scapular posterior tilt movement on the selective activation of the LT muscle during prone shoulder extension. Objectives: To examine the influences of additional scapular posterior tilt on electromyography (EMG) of the upper trapezius (UT) and the LT muscles during prone shoulder extension. Design: Cross-sectional study. Methods: There were 15 asymptomatic male participants in this study who performed prone shoulder extension with and without scapular posterior tilt movements. For the scapular posterior tilt movements, participants performed visual biofeedback training for scapular movement using motion sensor. During the exercises, the EMG activity of the UT and LT was recorded using surface EMG system. Results: The EMG activity of the LT significantly increased during prone shoulder extension with scapular posterior tilt compared to that of general prone shoulder extension, whereas that of the UT was not significantly different between the two exercises. Moreover, scapular posterior tilt application significantly decreased UT/LT muscle activity ratio. Conclusion: Scapular posterior tilt movement may be emphasized during exercise when facilitating LT muscle activation.

Background: Shoulder horizontal abduction in the prone position (SHAP) has been reported as an effective exercise to strengthen the lower trapezius. However, the effects of pre-emptive scapular posterior tilt on scapular muscle activity and scapulohumeral movements during SHAP have not been examined. Objectives: To examine the effect of the addition of scapular posterior tilt on muscle activity of the trapezius and posterior deltoid, and scapular posterior tilt and shoulder horizontal abduction, during SHAP. Design: Cross-sectional study. Methods: Fifteen healthy male subjects performed two types of SHAP: general and modified SHAP (SHAP combined with pre-emptive scapular posterior tilt). To perform modified SHAP, pre-emptive scapular posterior tilt training was performed prior to the modified SHAP. Muscle activity of the middle and lower trapezius and posterior deltoid, and the amount of scapular posterior tilt and shoulder horizontal abduction, were measured during two types of SHAP. Results: Muscle activity of the lower trapezius and scapular posterior tilt was significantly increased during the modified SHAP, while muscle activity of the posterior deltoid and the amount of shoulder horizontal abduction were significantly decreased. However, the middle trapezius muscle activity did not change during the modified SHAP. Conclusion: The SHAP with pre-emptive scapular posterior tilt can be useful to strengthen the lower trapezius.

Background: Round shoulder posture, results from excessive flexed posture of the thorax, is defined as a position of scapular protraction, anterior tipping, and downward rotation. However, previous studies have focused on only passive position of the thorax during scapular posterior tilting (SPT) and have not reported on SPT combined with correction of flexed posture. Objects: The aim of this study was to compare effects of SPT and SPT with prone trunk extension (SPT + PTE) on activities of the lower trapezius, serratus anterior, and thoracic erector spinae and degree of posture in subjects with round shoulder and flexed posture. Methods: Fifteen subjects with round shoulder and flexed posture were recruited. The caliper was used to measure the degree of round shoulder and flexed posture. Electromyography was performed to collect data of muscle activities. Paired t-test was used to compare two exercise (α=.05). Results: When SPT + PTE was applied, the degree of round shoulder posture (p=.001) and flexed posture (p=.039) significantly decreased compared with that when SPT was applied. The lower trapezius activity significantly increased in the SPT + PTE condition compared with that in the SPT condition (p=.026). There were no significant differences in serratus anterior activity between SPT + PTE and SPT. The thoracic erector spinae activity significantly increased in the SPT + PTE condition compared with that in the SPT condition (p=.014). Conclusion: SPT + PTE might be one of the effective methods to enhance activities of lower trapezius and thoracic erector spinae, and to reduce round shoulder posture and flexed posture in subjects with round shoulder and flexed posture.

Background: The serratus anterior (SA) muscle is one of the important muscles in the upward rotation of the scapula when the arm is raised. Insufficient muscle activity of the SA can cause deformation of the shoulder rhythm resulting in shoulder pathology. Objects: This study intends to compare SA and upper trapezius (UT) activity during the conventional wall-slide and push-up plus exercises for SA muscle strengthening and the scapular upward rotation (SUR) exercise. Methods: A total of 30 subjects participated in this study, and we measured the muscle activity of the SA and UT muscles during the wall-slide, push-up plus and SUR exercises. The one-way repeated ANOVA was used to compare SA and UT muscle activities during the 3 exercises. Results: During the SUR exercise, SA muscle activity was 79.88% maximum voluntary isometric contraction (MVIC), which was significantly higher than its activity during the other 2 exercises. The UT muscle activity was 47.53 %MVIC during the SUR exercise, indicating a significantly higher UT muscle activity than during the other 2 exercises. Conclusion: These findings suggest that the SUR exercise can maximize SA muscle activity to strengthen the SA while keeping UT muscle activity at an appropriate level.

Background: Methods for exercising serratus anterior (SA) and upper trapezius (UT) muscles are important for the recovery of patients with various shoulder disorders, yet the efficacy of closed or open kinetic chain exercises have not yet been evaluated. Objects: The purpose of this study was to compare the activation of the SA and UT muscles during scapular protraction considering both closed and open kinetic chain exercises. Methods: Thirty subjects were randomly divided into experimental groups (closed kinetic chain exercise) and control groups (open kinetic chain exercise) in which scapular protraction was performed at 90° or 125° shoulder flexion. Electromyographic activity data were collected from the SA and UT muscles per position and exercise method. Results: Separate mixed 2-way analysis of variance showed significant differences in the activation of the SA (F1,28=6.447, p=.017) and the UT (F1,28=35.450, p=.001) muscles between the groups at 90° and 125° shoulder flexion. Also, the SA/UT ratio measures at 90° and 125° shoulder flexion significantly differed between the groups (F1,28=15.457, p=.001). That is, the closed chain exercise was more effective than open chain exercise for strengthening the SA muscle and controlling the UT muscle, 125° of shoulder joint was more effective than 90°. Conclusion: The findings suggest that scapular protraction with shoulder 125° flexion at the closed kinetic chain exercise may be more effective in increasing SA muscle activation and decreasing UT muscle activation as well as increasing the SA/UT ratio than open kinetic chain exercise.

Background: Scapular posterior tilt (SPT) is important in the prevention of abnormal scapular movement and pain during elevation of the arm. However, previous studies have overlooked increased upper trapezius (UT) muscle activity interrupting the normal force couple of scapular motion and compensation of levator scapulae (LS) muscle activated simultaneously with UT during SPT exercise. Objects: The purpose of this study was to compare the effects of modified SPT with depression exercise versus SPT exercise on serratus anterior (SA), lower trapezius (LT), UT, and LS muscle activities and the clavicular tilt angle, in subjects with rounded shoulder posture (RSP) and myofascial pain in the UT muscle region. Methods: Eighteen subjects with RSP were recruited and randomly allocated to 2 groups; 9 in the SPT group and 9 in the SPT with depression group. All subjects met the specific RSP criteria and had myofascial pain of UT region. Depending on the allocated group, subjects performed the assigned SPT exercise and EMG data were recorded during the each exercise. Clavicular tilt angle was defined as the angle between the line joining the medial and lateral end of the clavicle and a horizontal line. Results: The SA muscle activity was significantly greater in SPT with depression than with SPT exercise (p<.05). The UT, LS muscle activity and the clavicular tilt angle was significantly lower in SPT with depression than with SPT exercise (p<.05). Conclusion: These findings were insightful because the potential risk of pain from overactivation of the UT and LS was considered, in contrast with SPT exercise. SPT with depression exercise can be implemented as an effective method to facilitate scapular muscle activity for stability and to prevent myofascial pain in the neck and shoulder.

Background: Scapular winging is a prominence of the entire scapular medial border, mainly caused by insufficient activity of the serratus anterior (SA) and imbalance of scapulothoracic muscles. Push-up plus (PUP) exercise has been commonly used to increase SA muscle activity. The facilitation of abdominal muscle may affect scapular muscle activity by myofascial connections. Thus, the sequential activation of the turnk muscles is suggested to facilitate the transition of proper force from upper limb and restore force couple of scapular muscles. The abdominal drawing-in maneuver (ADIM) has been effective in improving activation of the deep trunk muscles during movement. Objects: The aim of this study was to determine the effect of ADIM on the activity of the upper trapezius (UT), lower trapezius (LT), and SA during PUP exercises in subjects with scapular winging. Methods: Fourteen men with scapular winging (determined as a of distance between the scapular medial border and thoracic wall over 3 ㎝) volunteered for our study. The subjects performed the PUP exercise with and without ADIM. Surface electromyography was used to collect the electromyography data of the UT, LT, and SA. A scapulometer was used to measure the amount of scapular winging. Results: SA activity was significantly greater and scapular winging significantly lower during the PUP exercise with ADIM than during those without ADIM. Conclusion: PUP exercise with ADIM can be used as an beneficial method to improve SA activation and to reduce the amount of scapular winging in subjects with scapular winging.

Background: The functioning of the serratus anterior (SA) muscle is essential to normal scapulohumeral rhythm during forward flexion (FF) of the shoulder. Also, SA weakness and overuse of the upper trapezius (UT) is observed in patients with shoulder dysfunction and trapezius myalgia. We designed a combination exercise involving FF and scapular protraction with resistance (CFFSP) to activate the SA muscle and to deactivate the UT muscle. Objects: The purpose of this study was to determine whether or not CFFSP would be more effective in activating the SA muscle than FF alone and FF with scapular protraction (FFP). Methods: Nineteen subjects (12 men and 7 women) participated in this study and performed FF, FFP, and CFFSP at 120°. Surface electromyography was applied to the SA, UT, and pectoralis major (PM) muscles, as was one-way analysis of variance (ANOVA) with repeated measures. Statistical significance was set at .05. Bonferroni adjustment was used to counteract the problem of multiple comparisons, with a statistical level of significance of .017 (.05/3). Results: A statistically significant difference was found in relation to the three positions for the SA muscle (p<.001) and the SA/UT ratio (p=.005) using ANOVA. Significantly different results, depending on the position, were also demonstrated using the Bonferroni post-hoc test for the SA muscle (FF=28.27±16.20, FFP=45.66±15.81, and CFFSP=62.4±27.21) and for the SA/UT ratio (FF=3.04±2.14, FFP=3.61±2.38, and CFFSP=5.95±3.01). Significant differences between the three positions was not found regarding the average amplitude of SA/PM muscle ratio (SA/PM: p=.060). Conclusion: We recommend the use of CFFSP to strengthen the SA muscle at 120°.

Background: Shoulder stabilization commonly involves two components: the glenohumeral stabilization exercise (GSE) and scapular stabilization exercise (SSE). Despite the fact that the shoulder stabilization has advantageous merit, to our knowledge, only a few studies have compared the superior of the GSE and the SSE. Objects: The purpose of this study was to assess the effects of GSE in patients with nonspecific shoulder pain. Methods: Thirty subjects with nonspecific shoulder pain were randomly divided into an experimental group and control group, each with 15 patients. The experimental group used an GSE, whereas the control group did SSE. All subjects were measured in shoulder stability, scapular symmetric alignment, pain, muscle power, and range of motion before and after the intervention. Results: GSE resulted in significantly better shoulder stability (p=.046, from 8.67±7.54 score to 13.93±9.40) in the experimental group compared with SSE in the control group. However, no significant effects were observed for scapular symmetric alignment including the angles of inferior scapular distance (p=.829) and inferior scapular height difference (p=.735), pain (p=.113), muscle power including shoulder flexion (p=.723) and abduction (p=.897) and range of motion including shoulder flexion (p=.853) and abduction (p=.472). Conclusion: These findings suggest that GSE may be more effective in increasing the shoulder stability than the SSE in patients with nonspecific shoulder pain, probably through a centralization effect on the shoulder mechanism.

Background: For the treatment of forward head posture (FHP) and forward shoulder posture, methods for strengthening scapular retractors and deep cervical flexors and stretching pectoralis and upper cervical extensors are generally used. No study has yet assessed whether suboccipital release (SR) followed by cranio-cervical flexion exercise (CCFE) (SR-CCFE) will result in a positive change in the shoulders and neck, showing a “downstream” effect. Objects: The purpose of this study was to investigate the immediate effects of SR-CCFE on craniovertebral angle (CVA), shoulder abduction range of motion (ROM), shoulder pain, and muscle activities of upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA) and LT/UT and SA/UT muscle activity ratios during maximal shoulder abduction in subjects with FHP. Methods: In total, 19 subjects (7 males, 12 females) with FHP were recruited. The subject performed the fifth phase of CCFE immediately after receiving SR. CVA, shoulder abduction ROM, shoulder pain, muscle activities of UT, LT, and SA, and LT/UT and SA/UT muscle activity ratios during maximal shoulder abduction were measured immediately after SR-CCFE. A paired t-test and Wilcoxon signed-rank test were used to determine the significance of differences in scores between pre- and post-intervention in the same group. Results: The CVA (p<.001) and shoulder abduction ROM (p<.001) were increased significantly postversus pre-intervention. Shoulder pain was decreased significantly (p<.001), and LT (p<.05) and SA (p<.05) muscle activities were increased significantly post- versus pre-intervention. The LT/UT muscle activity ratio was increased significantly post- versus pre-intervention (p<.05). However, there was no significant change in UT muscle activity and SA/UT muscle activity ratio between pre- and post-intervention (p˃.05). Conclusion: SR-CCFE was an effective intervention to improve FHP and induce downstream effect from the neck to the trunk and shoulders in subjects with FHP.

The purpose of this study was to investigate the effects of visual electromyography (EMG) biofeedback on the EMG activity of the lower trapezius (LT), serratus anterior (SA), and upper trapezius (UT) muscles, the LT/UT and SA/UT EMG activity ratios, and the scapular upward rotation angle during scapular posterior tilting exercise (SPTE). Twenty-four subjects with round-shoulder posture participated in this study. The EMG activities of the LT, SA, and UT were collected during SPTE both without and with visual EMG biofeedback. The scapular upward rotation angle was measured at the baseline, after SPTE without visual EMG biofeedback, and after SPTE with visual EMG biofeedback. The LT, SA, and UT EMG activities, and the LT/UT and SA/UT EMG activity ratios were analyzed by paired t-test. The scapular upward rotation angle was statistically analyzed using one-way repeated analysis of variance. If a significant difference was found, a Bonferroni correction was performed (p=.05/3=.017). The EMG activities of LT and SA significantly increased, and the EMG activity of UT significantly decreased during SPTE with visual EMG biofeedback compared to SPTE without visual EMG biofeedback (p<.05). In addition, the LT/UT and SA/UT EMG activity ratios significantly increased during SPTE with visual EMG biofeedback compared to SPTE without visual EMG biofeedback (p<.05). Significant increases were found in the scapular upward rotation angle after SPTE without and with visual EMG biofeedback compared to baseline (p<.017), and no significant differences were observed in the scapular upward rotation angle between SPTE without and with visual EMG biofeedback. In conclusion, SPTE using visual EMG biofeedback may be an effective method for increasing LT and SA activities while reducing UT activity.

The purpose of this study was to assess the influence of scapular alignment on the electromyographic (EMG) activity of the trapezius in people with a short pectoralis minor muscle. For the study, we recruited 15 volunteers who had positive results for short on a pectoralis minor muscle length test. We measured the EMG activity of the upper, middle and lower trapezius muscles. The participants lifted their dominant arm to ear level with the thumb up toward the ceiling in the prone position on a table with the shoulder at a flexion angle of 180 degrees and a horizontal abduction angle of 120 degrees. Scapula was manually aligned by an experienced physical therapist prior to arm lift for the scapular alignment condition. A paired t-test was used to compare the effects of scapular alignment on the EMG activity of the trapezius muscles. The EMG activity of the lower trapezius muscle was significantly increased during the test with the scapular alignment compared to that without scapular alignment (p<.05), while the upper trapezius and middle trapezius exhibited no significant difference between the two conditions (p>.05). The findings of this study suggest that a scapular alignment may alter the recruitment of the lower trapezius muscle during arm lifting in the prone position in people with a short pectoralis minor muscle.

This study was conducted to find the effects of scapular taping on muscle activities of the scapular rotators and upper trapezius pain in subjects with upper trapezius pain. Fifteen male subjects were recruited from Yonsei University for this study. Muscle activity of upper trapezius, lower trapezius, and serratus anterior was measured using surface electromyography. Visual analog scale was used for measuring upper trapezius pain. The subjects were asked to maintain shoulder flexion position with holding a 1 kg dumbbell in standing position. Scapular taping was applied over the muscle belly of the upper trapezius and attached parallel with the lower trapezius muscle fibers. For normalization, % maximal voluntary isometric contraction (%MVIC) was conducted. Paired t-test was applied to compare the muscle activities of scapular rotator and upper trapezius pain before and after applying the scapular taping. The muscle activity of the upper trapezius muscle and serratus anterior decreased significantly after tape application (p<.05). However, no significant difference was observed in lower trapezius muscle. The level of pain in the upper trapezius muscle significantly decreased after tape application (p<.05). The results of this study suggest that scapular taping can be used an additional therapy for reducing muscle activity of upper trapezius, serratus anterior and upper trapezius pain during shoulder flexion in patient with upper trapezius pain.

This study was carried out to compare the muscle activities of the shoulder stabilizers between persons with and without winging scapular during push-up plus exercise (adds the scapular protraction to the general push-up exercise). For this study, eleven males with winging scapular and eleven healthy males were recruited. Surface electromyographic (EMG) activity was recorded from the serratus anterior, upper trapezius, lower trapezius, infraspinatus, and pectoralis major while the subjects performed the push-up plus. Each push-up plus was subdivided into three phases according to the elbow position which was measured using the 3-D motion analysis system: elbow flexion (EF), elbow extension (EE), and shoulder protraction phases (SP). Two-way repeated measure ANOVA (phase group) were used for statistical analysis. There was significant phase by group interaction only on the EMG composition ratio of the serratus anterior (p>.05). The EMG composition ratio of the serratus anterior was significantly higher in SP than in either EF or EE however, it was not different between winging scapular and normal groups. For both groups, the EMG composition ratio of upper trapezius, lower trapezius, and pectoralis major was significantly different across the phases of push-up plus, but the infraspinatus EMG composition ratio was not. For both groups, in EF and EE phases, the EMG composition ratio of both pectoralis major and serratus anterior were relatively higher than that of other muscles. However, in both groups, the EMG composition ratio of the serratus anterior became much more predominant than that of the pectoralis major. In addition, infraspinatus activated greater than pectoralis major. These results showed that the push-up plus exercise is effective to selectively strengthen the serratus anterior for both individuals with and without winging scapular, but not equally effective for other shoulder stabilizers.

Altered scapular kinematics in the scapular joint is commonly believed to be a factor contributing to trunk posture. The purpose of this study was to analyze the muscle activity with several changes of the shoulder angle. Tests were performed on 10 male subjects by repeated measures. Each subject was measured while sitting in both erect and slouched trunk positions. In each sitting posture, a three-dimensional motion analysis measurement was used to measure thoracic angle and shoulder abduction angle. Measurements were taken with the shoulder abdcution angle at , , , , , and . By using surface Electromyography (EMG) electrodes, we recorded the activity of the upper trapezius, middle trapezius, lower trapezius, middle deltoid, and serratus anterior muscle while the subject held a 4 kg weight at each angle. The mean of root mean square (RMS) of EMG activity was calculated. The middle trapezius, lower trapezius, and middle deltoid muscle activity showed significantly higher results but serratus anterior muscle activity showed significantly lower results (p<.05). With the shoulder angle increased, the muscle activity was also significantly increased (p<.05). In conclusion, the thoracic spine posture significantly affects the scapular muscle during scapular plane abduction, and the slouched posture is associated with increased trapezius muscle activity and with decreased serratus anterior muscle activity.