Muscle imbalance in the shoulder joint results in poor shoulder posture (rounded shoulder, elevated scapula). It also increases shoulder pain due to poor alignment and poor connective tissue condition. In addition, it can create grinding and clicking sound while moving the arm.
What is the pattern of muscle imbalance in the shoulder joint?
Anterior muscle group is getting too tight and the posterior muscle group becomes too weak. Since the anterior muscle group is stronger, it pulls the humeral head forward leading to rounded shoulder posture. Under the condition, the posterior muscle group cannot activate muscle contraction resulting in shoulder joint instability.
Anterior muscle group: pectoralis major/minor, anterior deltoid, biceps
Posterior muscle group: posterior deltoid, infraspinatus, teres minor, rhomboid, middle/lower trapezius
What causes muscle imbalance?
- Sitting for a long time with a poor posture (rounded/ forward shoulder posture). In this position, the anterior muscle can be adapted into the short muscle length.
- Overusing the anterior muscle group. People use the front side muscles predominantly when lifting, carrying or typing during the day. The front side muscle group becomes tighter and stronger compared to the back side muscle. Back side muscle groups get relatively weaker than the front side muscle.
- Imbalanced gym workout routine. People do chest exercises more often than the back muscle strengthening such as bench press as opposed to seated row exercise.
- People don’t give enough chest stretching even though the anterior muscle group is getting tighter from overuse.
How does pain and grinding sound increase with shoulder muscle imbalance?
Due to muscle imbalance, the humeral head is placed forward since the anterior muscle groups pull the humerus bone forward (rounded shoulder). Then, tendons (biceps, anterior deltoid, pectoralis) make grinding sound against the humeral head while moving the arm.
Imbalance muscles create more scar tissue and trigger point
Once the agonist and antagonist muscle imbalance gets worse, it creates a large amount of myofascial restriction (adhesion, scar tissue) and trigger points. Trigger points are the main cause of musculoskeletal pain. It can generate radiating pain to the arm and hand when it flares up.
Shoulder treatment protocol
1. First of all, if there is pain in the local area, find the trigger point/ adhesion and release it. It will decrease the pain level significantly (trigger point therapy, myofascial release)
2. Perform anterior muscle group stretching (manual therapy, stretching, home exercise)
Do sustained stretching pectoralis, biceps and anterior deltoid muscle groups. Stretch the muscle group for a long time until the flexibility increases.
3. Perform posterior muscle group strengthening (theraband exercise, dumbbell exercise)
Back muscle strengthening program targeting rhomboid, middle, lower trapezius, latissimus dorsi.
Posterior shoulder muscles group strengthening: posterior deltoid, infraspinatus
4. Try stretching the chest muscles (pectoralis) and strengthening the posterior deltoid muscle. If there is a grinding sound in the shoulder, it will decrease the sound significantly.