Strength Profile of Scapular Muscles in Collegiate Students

Introduction

Scapula plays an important role in shoulder function requiring both significant mobility and stability.¹ Muscles such as levator scapulae, rhomboids, serratus anterior and trapezius are involved in rotational movements and scapular stabilization. The rhomboid muscles retract, elevate and rotate the scapula.² Functionally, these muscles stabilize the scapula and also play an essential role in actions such as pulling and throwing, particularly in overhead arm movement.³ The trapezius muscles are responsible for active movements such as side bending and turning the head, elevating and depressing the shoulders, and internally rotating the arm. They elevate, depress, and retract the scapula.³ The latissimus dorsi muscle is also active in moving the trunk forward and upward when the upper extremities are fixed overhead, as in climbing or performing an activity such as a chin-up.⁴ Overall, these muscles work together to ensure proper shoulder function and stability during various movements and actions.

There are certain ill effects of using electronic devices. Continuous usage of smartphone for more than four hours per day increases shoulder and para scapular pain, fatigue, decreases the strength of scapular adductor muscles in right dominant side and increases the strength of left side due to the sustained hyperactivity of left side during holding and static postures.⁵

Intrinsic muscles of scapula include the rotator cuff muscles, teres minor, scapularis, teres major which assist in the functions such as abduction, external and internal rotation of the glenohumeral joint and extrinsic muscles which include biceps, triceps and deltoid are also responsible for the rotation and stabilization of the scapula. For the normal shoulder functions and for maintaining the scapula in normal alignment, scapular stability is very important and also is scapular muscle strength. Scapular muscle strength helps in better shoulder performance. In young adults, this scapular strength may differ because of their lifestyles. There are normative values for strength of this scapular muscles. Carrying a backpack can also cause postural changes which appear as excessive forward head angle, forward shoulder and changed scapular position.⁶ Even carrying a rucksack on one side can cause scapular depression and downward rotation, causing weakness due to overstretching of the upper trapezius. Prolonged periods in the depressed scapular position, in particular, may lead to chronic upper trapezius pain. Muscle activity of the left trapezius was significantly higher than the right trapezius during the one strap rucksack condition.⁷

Collegiate students use mobile phone for long periods. Additionally, they use laptops, carry backpacks, indulge in gaming on cell phones and computers. During these activities, the scapula plays an important role in stabilizing shoulder complex and any deviation from posture can lead to over activity of muscles leading to strain. The strength of scapular muscles is essential to perform functional activities. For an efficient glenohumeral movement to occur, the scapular muscles should be positioned dynamically to the glenoid. Any weakness or dysfunction of the scapular musculature can alter normal scapular positioning and mechanics. There will be decreased neuromuscular performance and can also predispose the individual to glenohumeral joint injury when the scapula fails to perform its stabilization role and when the shoulder complex function is inefficient. Repetitive movements can cause injuries to shoulder and scapular regions during our day-to-day activities such as using arm to prop the head while lying down and injuries can also be caused because of physical forces by hitting or during any games. Even improper postures can lead to scapular muscle weakness. Improper stretching and strengthening of muscles during games and day-today activities can cause injuries to shoulder, neck and scapula. Lifting heavy weights on shoulders is also a primary cause for scapular winging. Thus the chances for a collegiate students to suffer scapular injuries and scapular muscle weakness are high. Therefore it is important to measure the scapular muscle strength of this population and compare it with normative strength measurement values.

For an effective arm movement, a coordinated movement between scapula and the humerus is required, which is termed as scapular humeral rhythm. Scapula is the centre of rotation of the humerus and also holds the humerus to the thoracic wall. Scapula helps in avoiding impingement by keeping the acromion from obstructing movements of the humerus during flexion and abduction. If the scapular muscles are weak, then it will lead to change in the alignment of scapula. Shoulder impingement is caused because of the larger scapular protraction and greater medial rotation. In scapular dyskinesis, the scapular biomechanics will be increased with scapular medial rotation and scapular anterior tilt along with some alteration in scapular upward rotation. All these alterations in biomechanics of scapula and problems related to shoulder such as impingement are caused because of the muscular weakness. The pateints with scapular dyskinesis can experience anterior shoulder pain and posterosuperior scapular pain, all of which can be avoided if the scapular muscle is adequately strengthened. There are no normative values for strength of scapular muscles in normal young adults.

Limited studies are available with respect to strength profile in collegiate students. Hence, there is a need to understand the strength profile of scapular muscles among college students.

Materials and Methods

A sample size of 111 was obtained using G power software (Version 3.1.9.2) with an input parameters of effect size 0.03, alpha error of 0.05 and power of 0.95.

Permission from the concerned authorities and the institutional research committee was obtained prior to the commencement of the study. Based on the inclusion criteria, men and women in the age range of 18-23 years, students with normal range of motion (ROM) in shoulder joint (Luttgen and Hamilton 1997) were included. Exclusion criteria were any recent fractures of upper limb, any kind of limited shoulder disorders, neuron disorders, participants with limited shoulder ROM due to pain and or stiffness.

Participants were recruited after obtaining written informed consent.

Standardization of procedure

A pilot study was conducted involving five subjects to standardize research protocol. Based on the interpretation and analysis, changes in the measurement procedure were made. It was observed that latissimus strength can be measured bilaterally using Lat Pulldown Machine (PLLA). All the tests and measurement procedures were standardized.

Recruitment of the participants

Hundred and eleven (N=111) students in the age group of 18-22 years were recruited based on the inclusion and exclusion criteria. The aim, procedure and instructions were explained to the participants prior in the best language understood and consent was taken from them. Initially, demographic data was recorded.

Procedure

Participants underwent a five minute warm up session which included stretching of upper limbs, arm crossover, lateral steps, side bends, arm circles, followed by a 5 minute cool down period. This involved shoulder stretch, triceps stretch, forward bend, overhead stretch, chest stretch.

Muscle strength assessment

Strength was measured for three consecutive times and after one muscle strength test, participant was given a 10 minute break after which the same process was repeated for other muscles. The strengths of both right and left rhomboids, trapezius middle, trapezius lower and bilateral latissimus dorsi muscles were measured using standardized measurement methods. Strength was assessed using hand held dynamometer (HHD) (MicroFET2 – make, model Hoggan Health Technologies Inc, Salt Lake City, UT, USA) for bilateral (B/L) rhomboids, middle trapezius, lower trapezius and for latissimus, 1RM test was performed by Lat Pulldown machine.

Procedure for assessment and recording for rhomboids muscle, middle trapezius, lower trapezius and latissimus

Position of the participant was maintained prone and head could be turned to either side for comfort. Shoulder was internally rotated and arm was abducted across the back with elbow flexed and hand resting on the back. Therapist was in standing position on the test side. Resistance was applied in downward and outward direction and the participant lifted the hand off the back maintaining arm position across back and at the same time applying resistance above the elbow 2 cm from the acromion process. For the middle trapezius, participants were asked to lie prone at the edge of the table. Shoulder was abducted to 90 degrees. Elbow was flexed to a right angle. Head was allowed to be turned to either side for comfort and the therapist was standing on the test side close to patient’s arm. Stabilization of the contra lateral scapular area was done to prevent trunk rotation and resistance was directed downward towards the floor. For lower trapezius, participant was asked to lie prone at the edge of the table. Shoulder was abducted to 145 degrees. Elbow was flexed to right angle. Head could be turned to either side for comfort and therapist was standing on the test side close to patient’s arm. The contralateral scapular area was stabilized to prevent trunk rotation and resistance was directed downward towards the floor. Participants raised the arm from table to at least the level of ear, held it strongly against resistance which was applied at just 2 cm below the acromion process. Latissimus strength was measured using 1 RM test using Lat Pulldown machine. Strength was measured for three consecutive times and after one muscle strength test, a 10-minute break was given. The same was repeated for other muscles and average of the values was considered for the analysis.

Results

A total of 56 men and 55 women were included in the study. The mean age of men was 20.5±8.60 years and the mean age of women was 20.81±4.65 years. Average BMI of men was recorded as 21.68±8.95 and women was 21.0±5.17.

Discussion

The study observed the strength profile of scapular muscles which provided an insight on the possibilities of the strength values that could be predicted among the young adults of varied population. This study reported that dominant side was stronger than the other side and men showed differences in scores when compared to women. There were no normative values available for young adults on strength of scapular muscles.

The present study results are in agreement with Cochrane et al. ⁸ who reported a significant increase in the shoulder protraction during smartphone use among university students. This shoulder protraction causes increased activation of scapular muscles⁹ which causes either increased or decreased strength of scapula. Sahrmann¹⁰ stated that the stabilizers of scapula plays a vital role in stabilizing the scapula and if scapula rotates upwards, the upper trapezius and lower trapezius will hold the scapula in position. Therefore weakness of these muscle will lead to winging of scapula. In order to increase the upper extremity function and for the coordinated muscle contractions, it is very important that scapula should be in ideal position.¹¹ Thus it is important to check the scapular muscle strength in a normal adult to perform maximum upper extremity functional activities.

Conclusion

From this study, it can be concluded that young men exhibited more strength compared to young women. As no data regarding normative values is available, the values obtained in our study cannot be compared to normal values. However, the analysis showed that right side has more strength in both men and women.

Ethics approval and consent to participate

The project “Strength Profile of Scapular Muscles in Collegiate Students” has been cleared and approved by the Institutional Ethical Committee of JSS Medical College, JSSAHER, formerly and JSS University, with reference JSSMC/IEC/110523/48NCT/2023-24.

Competing interests

The author declares no competing interests.

Conflict of interest

Nil

Funding & Acknowledgements

This study is a part of the main study funded by Rajiv Gandhi University of Health Sciences, Bangalore, India