The goal of this quasi-experimental study is to determine the effect of the self-administered Modified Sleeper-Stretch on the elasticity of the posterior and posteroinferior glenohumeral capsule in adult individuals of both genders who either have clinical history of non-specific shoulder pain in a single shoulder or have no history of shoulder pain at all, being the assessment made by means of shear wave elastography. The main hypothesis it aims to confirm is:

• A soft tissue stretching program, using the Modified Sleeper-Stretch, aimed at general adult population with history of nonspecific shoulder pain that has occurred with glenohumeral internal rotation deficit improves the elasticity of the posterior and posteroinferior glenohumeral capsules, showing no significant effect on general adult population without history of shoulder pain.

Researchers will compare the effect of the Modified Sleeper-Stretch in the elasticity of the posterior and posteroinferior glenohumeral capsule in individuals with history of shoulder pain applying the technique on the affected shoulder and comparing with the healthy shoulder. In healthy individuals the intervention will be made on a randomly assigned shoulder and the effect will be compared to the non-interventional shoulder. Finally, a comparison between groups will be made considering only the intervention shoulder to see if there are differences in the effect amongst healthy and affected individuals.

Participants will be asked to follow a self-administered Modified Sleeper-Stretch program consisting of the execution of the stretch three times, for thirty seconds each time, with thirty seconds between stretches, daily, for twenty-eight days.

Non-specific shoulder pain is the third most frequent among musculoskeletal pains. It causes functional limitation that can lead to capsular stiffness and restriction of movement. Interventions aimed at reducing posterior capsule stiffness may improve the symptoms of painful shoulder. Modified Sleeper-Stretch is credited with the ability to decrease posterior shoulder stiffness. Shear-wave elastography is an imaging technique capable of quantifying the stiffness of the posterior capsule of the shoulder.

The objective of this study is to determine the effect of a stretching program using Modified Sleeper-Stretch on the elasticity of the posterior and posteroinferior capsule of the glenohumeral joint in adult population with and without a history of non-specific shoulder pain, using shear-wave elastography.

A quasi-experimental pre-post study will be conducted over two experimental groups of 32 subjects each. The intervention will involve following a self-stretching program of the posterior region of the shoulder using modified sleeper-stretch for 28 days. The study subjects will be adult individuals with a history of non-specific shoulder pain in the first group and no history of shoulder pain in the second. The first group will follow the program on the affected shoulder, the second on a randomly assigned shoulder. The elasticity of the posterior and posteroinferior glenohumeral capsule will be measured by shear-wave elastography in both shoulders at the beginning of the intervention, at its completion and four weeks after the end of the intervention.

Inclusion Criteria:

• Male or female with clinical history of nonspecific shoulder pain on a single shoulder, who had GIRD of 15º or more, asymptomatic for more than one month and less than one year.
• Male or female with no history of shoulder pain.
• Age between 18 and 59 years.

Exclusion Criteria:

• Glenohumeral osteoarthritis.
• Labrum lesion, Bankart or Hill-Sachs lesion.
• Posterior instability of any of the shoulders.
• Evidence of joint hypermobility as defined by a Beighton Scale score greater or equal to 6.
• Rotator cuff tear.
• Fracture or surgery in the cervical region or in any of the upper limbs, except shoulders, if less than a year has passed since the episode.
• History of surgical intervention in any of the shoulders.
• Tumor growth in the shoulder region.
• Neuromuscular injuries with shoulder muscles motor involvement (myasthenia, spinal cord injury, spastic contracture, paresis).
• Inflammatory diseases (rheumatoid arthritis, psoriatic arthritis) affecting the shoulder region in state of outbreak.
• Metabolic or systemic diseases with potential to modify tissue elastic capacity.
• Diseases or injuries with contraindication to mobilization or physical exercise of the shoulder region.
• Inability to perform the stretch due to pain.

All the information obtained in the study will be only published on a statistical basis. Only the principial investigator of the study will be able to associate information of the study with any individual participant.