Chronic Shoulder Pain
Conditions
Keywords
Electromyography, Muscle activation, Musculoskeletal pain, Neuromuscular control, Rotator cuff, Shoulder rehabilitation, Therapeutic exercise, Infraspinatus, Shoulder external rotation, Shoulder adduction
Brief summary
The goal of this randomized crossover trial is to determine whether different levels of shoulder adduction pressure during an external rotation exercise change shoulder muscle activity in adults with chronic shoulder pain and adults without shoulder pain. The main question is whether adding a small amount of shoulder adduction pressure increases activity of the infraspinatus muscle without increasing activity of the deltoid muscles. Researchers will compare three levels of adduction pressure (0, 5, and 10 mmHg) during the same external rotation exercise. Participants will perform the three exercise conditions in a randomly assigned order while researchers measure shoulder muscle activity using surface electromyography.
Detailed description
Shoulder external rotation exercises are commonly used during shoulder rehabilitation to improve rotator cuff muscle function. Adding isometric shoulder adduction during external rotation may modify the activation of the muscles involved in the exercise, but the effect of different levels of adduction pressure has not been fully established in adults with shoulder pain. This study was designed to examine whether progressively increasing shoulder adduction pressure during external rotation changes shoulder muscle activation in adults with chronic shoulder pain and adults without shoulder pain. The study used a randomized crossover design, in which each participant performed the same external rotation exercise under three different levels of adduction pressure. The order of the experimental conditions was randomized and balanced to reduce potential effects related to the sequence of conditions. The study focused primarily on the activation of the infraspinatus muscle, while activity of the deltoid, latissimus dorsi, and middle trapezius muscles was also assessed. Muscle activity was recorded using surface electromyography during the experimental exercise. The study was conducted during a single laboratory session.
Interventions
BEHAVIORALShoulder External Rotation With 0 mmHg Adduction Pressure
Participants performed the shoulder external rotation exercise while maintaining 0 mmHg of isometric shoulder adduction pressure against a biofeedback wedge. The exercise was performed with the shoulder positioned at approximately 45 degrees of external rotation from 0 degrees of glenohumeral rotation.
BEHAVIORALShoulder External Rotation With 5 mmHg Adduction Pressure
Participants performed the shoulder external rotation exercise while maintaining 5 mmHg of isometric shoulder adduction pressure against a biofeedback wedge. The exercise was performed with the shoulder positioned at approximately 45 degrees of external rotation from 0 degrees of glenohumeral rotation.
BEHAVIORALShoulder External Rotation With 10 mmHg Adduction Pressure
Participants performed the shoulder external rotation exercise while maintaining 10 mmHg of isometric shoulder adduction pressure against a biofeedback wedge. The exercise was performed with the shoulder positioned at approximately 45 degrees of external rotation from 0 degrees of glenohumeral rotation.
Sponsors
Universidad de La Frontera
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
OTHER
Masking
NONE
Intervention model description
This randomized crossover trial included two clinical comparison groups: participants with chronic shoulder pain and pain-free participants. Within each group, participants were randomly assigned to one of six possible sequences of three experimental conditions involving 0, 5, and 10 mmHg of shoulder adduction pressure during the external rotation exercise. Each participant completed all three experimental conditions. Peak muscle activity was recorded using surface electromyography.
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Shoulder Pain Group (SPG): * Adults aged 18 years or older. * Medical diagnosis of chronic non-traumatic shoulder pain lasting more than 3 months. * Resting pain intensity of at least 2 cm on a visual analogue scale (VAS). * Ability to perform at least 130° of shoulder flexion, 90° of shoulder abduction, and 45° of shoulder external rotation. Pain-Free Group (PFG): * Adults aged 18 years or older. * No current shoulder or neck symptoms. * No shoulder or neck symptoms during the previous 2 years. * No previous medical consultation for shoulder or neck discomfort. * Full shoulder abduction and external rotation range of motion. * Ability to perform pain-free maximal isometric contractions during shoulder abduction and external rotation.
Exclusion criteria
Shoulder Pain Group (SPG): * History of neck or upper limb surgery. * History of glenohumeral instability or upper limb fracture. * Neck pain or pain in another segment of the upper limb. * Systemic diseases that could influence shoulder movement or muscle activation, including rheumatoid arthritis or neuromuscular diseases. * Physical therapy treatment during the previous year for pain in the affected upper limb.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Peak Surface Electromyographic Activity of Shoulder Muscles | Day 1. During each experimental condition (0, 5, and 10 mmHg) | Peak surface electromyographic activity of the anterior deltoid, middle deltoid, posterior deltoid, infraspinatus, latissimus dorsi, and middle trapezius during the shoulder external rotation exercise. Electromyographic activity was normalized to the maximum voluntary isometric contraction (MVIC) and expressed as a percentage of MVIC. |
Countries
Chile
Contacts
PRINCIPAL_INVESTIGATORGermán Gálvez García, PhD
Universidad de La Frontera
Outcome results
None listed