Background: The serratus anterior (SA) is a muscle that performs protraction of the scapulothoracic joint and plays a role in stabilizing the scapula. Imbalances or weaknesses in SA activation are associated with a variety of shoulder dysfunctions, making selective SA strengthening important for rehabilitation. Objects: We aimed to compare the muscle activation of the pectoralis major (PM), SA, external oblique (EO), and internal oblique (IO) during the push-up plus (PUP) exercise with isometric hip adduction (HA) and abdominal drawing-in maneuver (ADIM). Methods: Nineteen healthy male participants performed three PUP exercises: standard PUP, PUP with ADIM, and PUP with HA. Surface electromyography was used to measure and analyze the muscle activity for PM, SA, EO, and IO. Results: PUP with HA showed the lowest PM activity and highest SA activity, and no significant difference was observed between PUP and PUP with ADIM. PUP with ADIM showed significantly the highest EO and IO activity, followed by PUP with HA and PUP. Additionally, PUP with HA showed the lowest PM/SA ratio, and no significant difference was noted between PUP and PUP with ADIM. Conclusion: PUP with HA was able to show high SA muscle activity while reducing PM muscle activity. In addition, PUP with HA can lead to higher EO and IO muscle activity than standard PUP. This exercise could be used as a practical exercise method to selectively strengthen SA and improve scapular muscle stability during early shoulder rehabilitation.

Background: The CKCUES test evaluates the functional performance of the shoulder joint. The CKCUES test scores CKC exercises of the upper limbs to examine shoulder stability. Although the CKCUES test provides quantitative data on functional ability and performance, no study has determined the relationship between CKCUES scores and SA and TB muscle strength. Objects: The objective of this study is to determine the relationship between the CKCUES test scores and the strength of the SA and TB muscles in the CKCUES and unilateral CKCUES tests. Methods: Sixty-six healthy male volunteers participated in the study. A Smart KEMA strength sensor measured SA and TB muscle strength. Two parallel lines on the floor indicated the initial hand placement to start CKCUES tests. For 15 seconds, the subject raises one hand and reaches over to touch the supporting hand, then returns to the starting position. Results: The correlation between the CKCUES test scores and the strength of the SA was strong (r = 0.650, p < 0.001), and the TB was moderate (r = 0.438, p < 0.001). The correlation between the unilateral CKCUES test and the strength of the SA of the supporting side was strong (r = 0.605, p < 0.001), and swing side was strong (r = 0.681, p < 0.001). The correlation between the unilateral CKCUES test and the strength of the TB of the supporting side was moderate (r = 0.409, p < 0.001), and swing side was moderate (r = 0.482, p < 0.001). Conclusion: Our study showed that the CKCUES test had a strong association with isometric strength of SA and moderate association with that of TB. These findings suggest that the CKCUES test can evaluate the function of the SA. Moreover, the unilateral CKCUES test can evaluate unilateral shoulder function.

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: The serratus anterior is one of the most important muscle for maintaining good scapular alignment in the shoulder joint. The pectoralis major and upper trapezius may also compensate for weak serratus anterior muscles. The push-up plus exercise has been identified as the optimal exercise for maximum activation of the serratus anterior. Objects: The purpose of this study was to examine differences in surface electromyography (EMG) activity of upper trapezius, pectoralis major, and serratus anterior muscles during push-up plus exercises on variously angled surfaces in subjects with winged scapula. Methods: Sixteen subjects with winged scapula (male=5, female=11) volunteered for this study. The subjects performed push-up plus exercise on four different tilt angles, namely 0˚, 30˚, 60˚, and 90˚. EMG activities in the serratus anterior, upper trapezius, and pectoralis major muscles during performance of push-up plus exercise were measured in all subjects. Data were processed from repeated measures one-way analysis of variance. Results: There was significant difference in the muscle activity of the serratus anterior on the different surface angles (p＜.05). The results of the post-hoc analysis showed significantly greater serratus anterior muscle activity on a surface at a 0˚ angle than at others tilt angles (p＜.05). There was also significant difference in the ratio of serratus anterior to upper trapezius and serratus anterior to pectoralis major across the four surfaces (p＜.05), and post-hoc analysis showed significantly greater values on the 0˚ surface than on other tilts (p＜.05). Conclusion: This study found that performing push-up plus exercises on a flat surface with 0˚ and 30˚ tilt angle achieves high activation of the serratus anterior muscle for selective strengthening. It can also take into account the sequential application, which is first performed at a 30˚ and at a 0˚ tilt angle for and effective but not excessive muscle activation.

Winged scapular (WS) causes muscle imbalance with abnormal patterns when moving the arm. In particular, the over-activation of the upper trapezius (UT) and decrease in activity of the lower trapezius (LT) and serratus anterior (SA) produce abnormal scapulohumeral rhythm. Therefore, the SA requires special attention in all shoulder rehabilitation programs. In fact, many previous studies have been devoted to the SA muscle strength training needed for WS correction. Objects: The purpose of this study was to investigate the effect of shoulder girdle muscle and ratio according to the angle of shoulder abduction and external weight in supine position. Methods: Twenty three WS patients participated in this experiment. They performed scapular protraction exercise in supine position with the weights of 0 ㎏, 1 ㎏, 1.5 ㎏, and 2 ㎏ at shoulder abduction angles of 0˚, 30˚, 60˚, and 90˚. The angle and weight applications were randomized. Surface electromyography (EMG) was used to collect the EMG data of the SA, pectoralis major (PM), and UT during the exercise. The ratio of PM/SA and UT/SA was confirmed. Two-way repeated analyses of variance were used to determine the statistical significance of SA, PM, and UT and the ratios of PM/SA and UT/SA. Results: There was a significant difference in SA according to angle (p<.05). Significant differences were also identified depending on the angle and weight (p<.05). The angle of abduction at 0˚, 30˚ and weight of 2 ㎏ showed the highest SA activity. However, there was no significant difference between PM and UT (p>.05). There was a significant difference between PM/SA and UT/SA in ratio of muscle activity according to angle (p<.05). Significant differences were found at PM/SA angles of 30˚, 60˚ and 90˚ (p<.05). For UT/SA, significant difference was only observed at 90˚ (p<.05). Conclusion: Based on the results of this study, in order to strengthen the SA, it was found to be most effective to use 1 and 1.5 ㎏ weights with abduction angles of 0˚ and 30˚ at shoulder protraction in supine position.

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: 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°.

The aim of this study was to compare the activity of the upper trapezius (UT) and serratus anterior (SA) and ratio of UT to SA during shoulder elevations. Ten subjects with UT pain (UTP) and 13 subjects without UTP participated in this study. Subjects with a UTP of over five in a pain intensity visual analogue scale (0-10 ㎝) for more than 2 months and latent myofascial trigger points (MTrPs) in the UT muscle were included in the UTP group. Electromyography (EMG) data of UT and SA at 1st and 10th elevations were analyzed. Two-way repeated analyses of variance were used to compare the EMG activity of UT and SA and the ratio of UT to SA during shoulder elevations between groups with and without UTP. There was a significant increase in UT/SA ratio in the group with UTP compared to the group without UTP (p=.01). The activity of UT and SA measured at the 10th elevation was significantly greater than that in the first elevation (p<.05). The activity of SA was significantly greater in the group without UTP than the group with UTP (p=.03). However, there was no significant difference between groups with and without UTP in terms of UT activity (p=.28). These results indicate that UTP may have relevance to the increased muscle activity ratio of UT to SA during shoulder elevations.

Push-up plus has been advocated for increasing the activity of the serratus anterior muscle, the most critical scapular stabilizer. However, no previous study has reported the possibility of compensatory motion on the part of the pectoralis major, which could substitute for the action of the serratus anterior during push-up plus. The aim of the current study was to investigate the immediate effect of electromyography (EMG) biofeedback of the pectoralis major muscle on the pectoralis major, upper trapezius, and serratus anterior muscles during push-up plus. Fourteen healthy young subjects voluntarily participated in this study; each subject performed push-up plus from the quadruped position, in two conditions (i.e., with or without visual and auditory biofeedback). Surface EMG was used to measure pectoralis major, serratus anterior, and upper trapezius activity. A paired t-test was used to determine any statistically significant difference between the two conditions. Additionally, effect size was calculated to quantify the magnitude of EMG biofeedback in each muscle. Visual and auditory feedback reduced pectoralis major muscle activity significantly (p=.000) and increased the serratus anterior muscle activity significantly (p=.002), but did not induce a significant difference in upper trapezius muscle activity (p=.881). Thus, it is concluded that the visual and auditory feedback of pectoralis major muscle activity can be used to facilitate serratus anterior muscle activity during push-up plus.

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.

The purpose of this study was to investigate the effects of serratus anterior strengthening exercises on scapular position and Visual Analog Scale (VAS) pain measurements taken at the resting position in young adults with adducted scapular. The exercise program included stretching of the scapular retractor and strengthening of the serratus anterior muscle. We measured the distance from the midline of the thorax to the vertebral border of the scapular with a tape line (Superior Kibler), and the distance from the 7th cervical spinous process to the acromial angle with 3-dimension motion analysis system, to compare the resting scapular position before and after exercise. Fifteen subjects with adducted scapular were recruited to compare the resting scapular position and VAS. The distance from 7th cervical spine process to acromial angle of the scapular and VAS decreased significantly (p<.01) after exercise, while the distance from the midline of the thorax to vertebral border of the scapular increased (p<.05). The conclusion is that the serratus anterior exercise program altered the resting scapular position and decreased VAS.