Correlation of Glenohumeral Internal Rotation Deficit with Scapular Dyskinesis and Posterior Shoulder Muscle Endurance in serving arm of tennis athletes

GIRD of the playing arm is a predictor of risk for injury in overhead athletes. It has an effect

on dynamic scapular positioning which provides a stable base for efficient functioning of the

arm and in turn an injury-free performance by the athlete. GIRD may affect posterior muscle

endurance due the mis-match in length-tension relationship of posterior and anterior

muscles. It is therefore essential to further evaluate these links in preventing shoulder

injuries, enhancing performance and increasing longevity of playing years. 47 participants will

be selected on the basis of inclusion and exclusion criteria. Informed consent will be taken

and if they agree to participate in this study, they will be included in the study. A study of 15-

20 minutes will be performed. They will be asked about their demographic data (name, age,

etc). Glenohumeral internal rotation deficit will be assessed by measuring the difference of

internal rotation range between the serving and non-serving arm using an inclinometer in arm

abduction of 90º and elbow flexion of 90º in prone. Scapular dyskinesis is a computation of

Scapular protraction and anterior tilting and scapular upward rotation. Scapular protraction

and anterior tilting are measured by Pectoralis Minor Index which is the division of pectoralis

minor length (inferomedial aspect of coracoid process and caudal end of 4th rib at sternal

end) in cm by participant’s height in cm multiplied by 100. Scapular Upward Rotation angle is

measured by using 2 inclinometers; one at distal humerus to estimate abduction angle at of

0º, 45º, 90º, 135º and end range abduction; another at spine of scapula. Next, Posterior

shoulder muscle endurance is calculated by Shoulder Endurance Test which is performed by

the serving arm that will be placed in 90º forward flexion (starting position); holding a 1-m

long Thera-band fixed at shoulder height on a graduated stick, which will be placed 2 metres

from ending position (90º external rotation and 90º abduction) allowing a 100% stretch of

length of Thera-band. Males will be asked to pull green Thera-band (2.1 kg) and females a red

Thera-band (1.7 kg) and a metronome will be used to determine the cadence that will be

increased by 30 bpm every 20 seconds starting from 60 bpm to 150 bpm (60-90-120-150) and

will remain same till the end of the test. Time till the test is terminated will be calculated in

seconds and fatigue score will also be asked. Proper rest will be given between each test.

Once all data is collected, it will be analysed using the statistical tests. Depending upon the

normality of the data, Pearson’s or Spearman’s coefficient will be calculated.