The well-coordinated movement of the scapula and glenohumeral joint plays a crucial role in shoulder movement. Dysfunction or weakness of the scapular stabilizers and insufficient mobility of the scapula often lead to altered biomechanics, which can result in abnormal stress on the anterior capsular structures, increased risk of rotator cuff compression, and decreased performance.1,2 In addition to the scapula, the range of motion (ROM) of the glenohumeral joint is important in overhead sport.3 Notably, external rotation is essential for pitching and throwing. According to research on pitchers, preseason limitations in external rotation and flexion ROM significantly increase the risk of elbow injuries in subsequent seasons.4 Shortening of the anterior chest muscles can reduce the posterior tilt of the scapula and external rotation of the glenohumeral joint, thereby affecting the scapulohumeral rhythm.5 Therefore, clinicians, athletic trainers, and strength and conditioning coaches conduct various exercises to improve scapular mobility and stability in individuals. However, it is critical to evaluate and understand the current problematic situation and then to facilitate recovery through corrective exercises.
The KOJI AWARENESS (KA) screening test, which does not require specific tools, assesses strength and flexibility across 11 components of total musculoskeletal function.6–9 It also identifies problematic areas, which are targeted with KA corrective exercises to aid in the recovery from dysfunction or pain.10,11
For the scapular exercises, scapular upward rotation and shrug exercises are effective in addressing scapular downward rotation syndrome.12,13 The Wall Angel Slider exercise is a KA corrective exercise aimed at mobilizing the scapula, linked to the KA Self-Screening Scapula Mobility Test.10 It involves a reverse action method instead of moving the arms upward and downward.
Therefore, in this study, we aimed to investigate whether the KA Original Wall Angel Slider exercise can effectively improve scapular upward rotation and glenohumeral joint external rotation ROM over a 2-week intervention period followed by KA screening test. We hypothesized that this exercise would effectively improve scapular and glenohumeral joint external rotation ROM in individuals with limited scapular mobility over a short period. If the Wall Angel Slider exercise is proven effective, it could be a valuable option for athletes or patients seeking new exercises that involve reverse motion tasks.
Materials and Methods
Participants
This study was conducted at fitness centers affiliated with our institutions between October 2019 and March 2022. Ethical approval was obtained from the Research Ethics Committee of Tokyo Medical and Dental University (research protocol identification number: M2019-168). All participants provided written informed consent before undergoing scapular ROM assessment. Fifty-four participants were enrolled in this study (Table 1). The participants were advised to wear a comfortable athletic outfit that allowed for unrestricted movement. Individuals with any injuries within the last 3 months were excluded. In addition, the participants were instructed to discontinue the assessment if they experienced pain. However, none of the participants withdrew from this study because of injury or discomfort.
Participant Demographics
| Status | |
|---|---|
| Gender, female:male | 18:27 |
| Age, ya | 27.0 (11.0) |
| Height, cm | 168.5 (8.4) |
| Weight, kga | 69.3 (20.3) |
| BMI,a kg/m2 | 24.1 (5.2) |
Abbreviation: BMI, body mass index.
aData are represented as medians (interquartile ranges).
Procedures
All participants underwent a screening process using the KA Scapular Mobility test to confirm scapular mobility restriction. The test instructions are shown in Figure 1. Six participants without scapular mobility restriction were excluded from further analysis. The remaining 48 participants (18 females and 27 males) commenced the Wall Angel Slider exercise program. To ensure accurate execution of the exercise, all participants received detailed instructions and underwent a technique assessment at the fitness center during the first session, conducted by a certified athletic trainer from a Board of Certification for the athletic trainer, after the initial week of the intervention. After the first exercise session, the participants were instructed to complete a 2-week exercise intervention at home, with 6 sessions completed 3 days weekly. Each session included 3 sets of 8 repetitions. Adherence to the exercise program was monitored using a checklist provided to the participants. Also, participation in the sports activities that might affect the mobility of the scapula and shoulder joint, such as baseball, was monitored, and no participants joined the sports. An certified athletic trainer assessed the scapular and glenohumeral external rotation ROM at 3 time points: before the intervention, immediately after the first session on the first day, and after the 2-week intervention period.
Study protocol and inclusion and exclusion criteria. KA indicates KOJI AWARENESS; ROM, range of motion.
Citation: Journal of Sport Rehabilitation 2025; 10.1123/jsr.2024-0426
The KA Self-Screening Scapula Mobility Test
The KA Self-Screening Scapula Mobility test was developed to evaluate scapular mobility.6 Details regarding this scapular mobility screening test is available from the Japan Sports Agency website and YouTube (https://www.youtube.com/watch?v=h4HQXcCLheg&t=74s [accessed on December 8, 2024]). Instructions are shown in Figure 2. First, the participants were instructed to stand in front of a mirror. The arm on the measured side was bent and horizontally adducted with the fingertips holding the opposite earlobe. The participants were then instructed to move their arms over the head and back to the starting position while holding their earlobes. The criterion for successful completion was the arch of the arm completing the movement around the head and returning without the head tilting. The assessment of each participant was supervised by the certified athletic trainer.
Explanation of KOJI AWARENESS Self-Screening Scapula Mobility Test. Setup: stand in front of a mirror with fingertips holding opposite earlobe. Movement: move the arm around the head and back. Goal: arch of the arm goes around the head and comes back without tilting the head.
Citation: Journal of Sport Rehabilitation 2025; 10.1123/jsr.2024-0426
Scapular Upward Rotation ROM Test
The participants were instructed to elevate both arms with full elbow extension into maximum abduction during bilateral standing. The angle of the spine of the scapula relative to the midline was measured using a goniometer (R-360-W International Goniometer, Tiger Medical Instruments).14 A previous study reported a reliability of the measurement method (the intraclass correlation coefficient of .94).15 The measurement was repeated thrice, and the average angle was calculated (Figure 3).
Scapula upward rotation range of motion test. Both arms were elevated with full elbow extension into maximum abduction during bilateral standing, and the angle of the medial border of the scapula relative to the midline was measured using a goniometer.
Citation: Journal of Sport Rehabilitation 2025; 10.1123/jsr.2024-0426
Glenohumeral External Rotation ROM Test
Shoulder external rotation ROM was measured in the supine position. The participants were instructed to lie on the treatment table, and the measured side of the shoulder was positioned at 90° abduction. The examiner passively moved the shoulder joint to maximum external rotation and measured the angle using a goniometer. The intraclass correlation coefficient of .97 for the intratester and .90 for the intertester reliabilities were reported.16 The external rotation angle was measured thrice, and the average angle was calculated (Figure 4).
Glenohumeral external rotation range of motion test. The shoulder external rotation range of motion was measured in the supine position, and the measured side of the shoulder was positioned at 90° abduction. The examiner passively moved the shoulder joint to the maximum external rotation and measured the angle using a goniometer.
Citation: Journal of Sport Rehabilitation 2025; 10.1123/jsr.2024-0426
Wall Angel Slider
The Wall Angel Slider is a KA corrective exercise aimed at improving scapular mobility.10 We suggested to the participants that they obtain information about this corrective exercise from a YouTube video accessible on the Japan Sports Agency website ( https://www.youtube.com/watch?v = DsJIWK_iyOM [accessed on December 5, 2024]) to check the correct form of the exercise (Figure 5). It involves a reverse action method instead of moving the arms upward and downward, requiring participants to maintain the wrist, elbow, scapula, and back on the wall; perform slide squats down toward the ground; and return. In order to maintain the arm position on the wall with the scapula adduction and posterior tilt and upright trunk position while squatting down and up, it is speculated that scapula girdle and trunk muscles activate. In addition, scapula elevator and shoulder abductor muscles, such as the upper trapezius and deltoid, may be inhibited due to no active elevation of the arms. Furthermore, the Wall Angel Slider exercise offers clear recognition of the relative position among the arm, shoulder, scapula, and trunk, and the direction of the movement from the tactile stimulation of the wall provides feedback for the alignment of the body. A previous study reported that the tactile feedback is important for adjusting the motor command.17 Therefore, the exercise with tactile feedback can result in effective stretching and muscle activation.
Wall Angel Slider. The Wall Angel Slider exercise involves a reverse action method instead of moving the arms upward and downward, requiring participants to maintain the wrist, elbow, and back on the wall; perform slide squats down toward the ground; and return.
Citation: Journal of Sport Rehabilitation 2025; 10.1123/jsr.2024-0426
Statistical Analyses
Statistical analyses were performed to assess the normality of the variable distributions using histograms and the Shapiro–Wilk normality test. Descriptive statistics are presented as mean (SD) and medians (interquartile range) for normally and nonnormally distributed variables, respectively.
Friedman test was performed to compare the scapular upper rotation and glenohumeral external rotation ROM at different time points. Wilcoxon signed-rank test was used as a post hoc test for main effects. For the effect size (ES), r value was calculated in the post hoc test. r values of .10 to .29, .30 to .49, and ≥.50 correspond to small, medium, and large effects, respectively. Statistical analyses were performed using IBM SPSS Statistics (version 27 for Windows), and statistical significance was set at P = .05. For the post hoc test, the significance level was set at .0167% with Bonferroni adjustment.
Results
Six participants were excluded after the initial scapular mobility assessment using the KA Self-Screening Scapula Mobility Test owing to the absence of scapular mobility restrictions. Therefore, 48 participants participated in the Wall Angel Slider home exercise program for 2 weeks. No participants were excluded due to insufficient exercise implementation confirmed by an exercise checklist. Three participants did not attend the ROM assessment after the 2-week intervention period. Forty-five participants were assessed for scapular upward rotation and glenohumeral external rotation ROM (Table 2).
Changes in the ROM of Scapular Upward and Shoulder External Rotation After the Intervention
| Preintervention | After the first exercise session | Postintervention | |
|---|---|---|---|
| ROM: scapula upward rotationa | 55.0 (12.5) | 65.0 (10.0)b | 65.0 (10.0)b |
| ROM: shoulder external rotationa | 100.0 (17.5) | 105.0 (12.5)b | 107.5 (20.0)b |
Abbreviation: ROM, range of motion.
aData are represented as median (interquartile range). bCompared with preintervention.
In the Friedman test, there were main effects in scapular upward rotation and glenohumeral external rotation (P = .002 and P < .001, respectively). Changes in the scapular upward rotation and glenohumeral external rotation ROM are presented in Table 2. Scapular upward rotation significantly improved immediately after the first exercise session (by 5.4°; P < .001, ES = 0.55) and after the 2-week intervention period (by 7.6°; P < .001, ES = 0.60) compared with the baseline value. Similarly, glenohumeral external rotation significantly improved immediately after the first session (by 3.4°; P = .001, ES = 0.51) and after the 2-week intervention period (by 3.2°; P = .002, ES = 0.46) compared with the baseline value. No significant differences in scapular upward and glenohumeral external rotations were observed between after the first exercise session and postintervention.
Discussion
In the present study, we assessed the effectiveness of the KA Original Wall Angel Slider exercise in improving scapular ROM over a 2-week intervention period. We hypothesized that this exercise would significantly improve scapular upward rotation and glenohumeral joint external rotation ROM within the given timeframe. The results of this study align with our hypothesis as significant improvements in scapular ROM were observed after the intervention.
Scapular mobility is restricted by the shortening or tightening and dysfunction of the shoulder girdle muscles. The pectoralis minor is often targeted to improve scapular mobility in patients with shoulder pain or athletes. In a previous study, a short pectoralis minor at rest resulted in altered scapular kinematics during arm elevation.18 The lower trapezius and serratus anterior play crucial roles in actively controlling scapular motion and should be reconditioned before the rotator muscles in overhead sport athletes with shoulder pain.19 In previous studies, scapular upward rotation exercises effectively improved scapular and clavicular alignment and increased the strength of scapular upward rotator muscles in individuals with scapular downward rotation syndrome.12,13 In addition, a previous study described that a single session of a passive pectralis minor stretching, which has an upper-limb position similar to the exercise in this study, improved scapula motion compared with the no intervention group.20 Similar to the results of previous studies, the Wall Angel Slider exercise in the present study improved the scapular upward rotation ROM. Therefore, the Wall Angel Slider exercise may lead to better scapular mobility compared with no intervention. The advantage of this exercise is that it involves a reverse action method in which the body is lowered while maintaining the arm position on the wall instead of elevating the arms. Because of the reverse action method, the effort required for arm elevation in this exercise is less than that required in conventional scapular exercises, and the hyperactivity of the upper trapezius, which is often present in overhead sport athletes with shoulder problems,21 can be inhibited. In addition, maintaining the wrist and elbow positions on the wall provides tactile stimulation to recognize the proper posture while lowering the body. Tactile stimulation is important feedback for adjusting the motor command.11 This tactile feedback might lead to clear recognition of the scapular adduction and glenohumeral joint horizontal abduction, which can effectively stretch the pectoralis minor. Furthermore, scapular adduction during exercise may result in activation of the middle- and lower-trapezius muscles. Because of proper stretching and facilitation of the muscles, the Wall Angel Slider exercise may improve scapular upward rotation ROM.
External rotation of the glenohumeral joint was also improved using this intervention. Because the wrist and elbow are placed on the wall behind the back, the glenohumeral joint assumes an external rotation position during exercise. Maintaining this position requires continuous activation of external rotators, such as the infraspinatus and teres minor. Muscle contraction results in reciprocal inhibition of antagonist muscles.22 Continuous contraction of the external rotators may inhibit the pectoralis major, subscapularis, and latissimus dorsi muscles. Given that these muscles are inhibited during the Wall Angel Slider exercise, the effect of stretching on the external rotators could be enhanced. Therefore, glenohumeral external rotation ROM was improved after the intervention.
Improvement in scapular upward rotation and glenohumeral external rotation ROM was observed after the first exercise session and after a short intervention period. In a systematic review, stretching of the posterior shoulder muscles had positive immediate and short-term effects.23 The intervention period in this study was only 2 weeks. This might be because the Wall Angel Slider exercise is not a passive stretch exercise but an active exercise. Activation of the scapular upward and glenohumeral external rotators with stretching of the antagonist muscles may lead to modification of the motor control pattern. In a previous study, passive stretching or mobilization was less effective for motor learning.24 Therefore, activation and stretching of the muscles in proper alignment, confirmed using tactile feedback, might improve ROM in a short period or even after a session.
Clinical Implications
The KA Original Wall Angel Slider exercise involves a reverse action method, which may be particularly beneficial to individuals experiencing difficulties in raising their arms, such as those in rehabilitation after surgery. Performing exercises against gravity can be challenging; however, this method offers various shoulder blade exercises. Overactivation of upper trapezius fibers can lead to inefficient shoulder movements and pain. This reverse action method can help train the body to raise the arms with reduced activation of the upper trapezius and deltoid muscles. It can be used as a technical exercise for activities, such as throwing, freestyle swimming, and serving in tennis. By incorporating this unique approach, the Wall Angel Slider exercise offers an alternative for individuals with limited arm mobility, potentially enhancing their ability to effectively perform therapeutic exercises. Furthermore, the Wall Angel Slider may help the trunk muscles to maintain posture while performing the exercise. Because the trunk is the base of the scapula, coordination of the trunk and shoulder girdle muscles is essential for shoulder function. The facilitation of well-coordinated activity between the trunk and shoulder girdle muscles is beneficial for enhancing the performance of overhead sport athletes.
Limitations
This study has some limitations. First, it did not include a comparison group, such as a conventional scapular exercise with arm elevation. Because there was no comparison with other intervention or control groups, the advantage of the Wall Angel Slider exercise remains to be elucidated. Second, only healthy participants with scapular upward rotation restriction were recruited in this study. Patients and athletes with shoulder disorders may exhibit different scapular kinematics. Furthermore, pain and other symptoms may influence exercise implementation. Third, the intervention period was only 2 weeks. Longer periods of intervention may result in different results. However, the findings of this study provide valuable information that scapular upward rotation and glenohumeral external rotation ROM can be improved over a 2-week intervention period.
Conclusion
The results of this study revealed that the Wall Angel Slider exercise, which is one of the KA corrective exercises, could improve scapular upward rotation and glenohumeral external rotation ROM within 2 weeks. The findings of this study suggest that exercises involving the reverse action method may be beneficial for correcting shoulder girdle function. Further studies are required to clarify the advantages of the Wall Angel Slider exercise through a randomized controlled trial of patients or athletes with shoulder problems for longer intervention periods.
Acknowledgments
Sources of Funding: This work was supported by the Japan Agency for Medical Research and Development (grant number: 23le0110027).
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