Scapulohumeral Rhythm

By: Chris Gellert, PT, MMusc & Sportsphysio, MPT, CSCS, AMS

The shoulder is one of the most vulnerable joints in the body due to its vast range of motion and complexity. It is a complex ball and socket joint, uniquely comprised of various connective tissue, supporting structures, including muscles. It is an important joint because functionally, it is involved in most daily and sport activities, such as reaching, lifting, carrying and throwing a ball. Knowledge of the biomechanics of the shoulder can help you with training and aiding in rehabilitation of the shoulder and related injuries.

The shoulder complex involves coordinated movements between the humerus bone and the scapula. The scapula, clavicle, and humerus serve as attachments for most of the muscles in the shoulder. The shoulder is comprised of four primary joints:

  • Glenohumeral joint (GH)
  • Acromioclavicular joint (AC)
  • Sternoclavicular joint (SC)
  • Scapulothoracic joint

 

 

 

Scapulohumeral Rhythm (SHR) is defined as the movement relationship between the humerus and the scapula during both shoulder flexion and shoulder abduction. Arthrokinematics is the movement that takes place between articular surfaces in a joint.

For example, during abduction of the arm at the shoulder (side arm raise) the following happens (See Figure):

  • The glenohumeral joint (concave) is stable (depicted by the vertical arrow), while the humerus (convex) abducts (depicted by the horizontal arrow).
  • There is a sliding down or glide of the convex humerus on the concave glenohumeral joint.
  • The scapula rotates upward (bottom of the scapula moves laterally and upward).

 

During shoulder abduction, there is 120 degrees of movement that occurs at the glenohumeral joint, while 60 degrees occurs at the scapulothoracic joint, creating a 2 to 1 ratio (2:1). This movement is known as the scapulohumeral rhythm (SHR) of shoulder abduction. The same SHR occurs both during shoulder flexion and shoulder abduction. (See Figure)

The muscle actions that occur when you abduct the arm at the shoulder include: (See Figure)

  • Biomechanically, the supraspinatus muscle raises the arm during the first
    15 degrees of shoulder abduction.
  • Then, from 15-90 degrees of shoulder abduction, the medial deltoid assists to raise the arm biomechanically.
  • There are several muscles within the shoulder that play important roles, specifically at the rotator cuff. The rotator cuff is comprised of four primary muscles known as the S.I.T.S muscles. These muscles include the supraspinatus, infraspinatus, teres minor and subscapularis which pull the bone in different directions due to different attachment points and angle of pull.
  • A force couple can be defined as a pair of muscle forces that act together on a joint to produce rotation. These forces may exert pulls in opposite directions. Force couples may be synergistic pairs or agonist/antagonist pairs of muscles.  In the Figure shown, a force couple occurs between the low trapezius and serratus anterior. During shoulder abduction, the lower trapezius and serratus anterior work together to anterior upwardly rotate the scapula on the thorax.

 

Abnormal scapulohumeral rhythm is a dysfunction that occurs within the scapulothoracic junction.  There are many causes for this including:

  • A rotator cuff tear where the individual does not have the musculotendinous connection and strength to abduct the arm.
  • Limitations due to joint and capsule hypomobility (restriction) known as adhesive capsulitis (frozen shoulder).
  • Pain and/or muscular weakness that prevent the ability to raise the arm to the side.
  • Occurrence of excessive upper trapezius and scapular elevation which becomes a means of compensation, and provides the individual with an alternative ability to abduct the arm.

Why is this important?

  • Connective tissue (muscles, tendons, ligaments, and fascia) are supposed to move. Joints, as well, have a certain amount of movement and should glide and translate with everyday movement.
  • Muscle imbalances and tightness create dysfunction. If a muscle does not have adequate muscle length to concentrically and eccentrically contract, compensation will occur typically above and below a joint.
  • If this tightness continues, it will result in trigger points. Trigger points are where a muscle shortens and, in essence, has increased sensitivity affecting the muscle’s ability to completely move as it was designed. If trigger points become bigger and more prominent, they can compress the nerve that innervates the respective muscle creating radicular (fuzzy feeling, numbness, or tingling) symptoms.

If the scapula is not able to properly upwardly rotate on the thorax, an individual will compensate using other muscles to perform the work. This compensation will lead to muscle imbalance, pain, and dysfunction affecting activities of daily living and sports movements.

For more information about working with clients with shoulder issues, see the Fitness Learning Systems Human Movement Matrix: Shoulder continuing education course by Chris Gellert, PT, MMusc & Sportsphysio, MPT, CSCS, AMS of Pinnacle Training & Consulting Systems.  www.pinnacle-tcs.com “Teaching The Science Behind The Movement.” Fitness Learning Systems is an IACET accredited continuing education provider.

5 Things to Know About Breast Cancer and Exercise

This information is adapted from the Fitness Learning Systems continuing education course Return to Life: Breast Cancer Recovery using Pilates, by Naomi Aaronson MA OTR/L CHT Certified Cancer Exercise Trainer, Ann Marie Turo OTR/L Yoga/Pilates Instructor, Reiki Master

In 2016, there are expected to be 246,660 new cases of invasive breast cancer and 61,000 new cases of ductal breast carcinoma in situ (DCIS). More than 2.8 million individuals have survived breast cancer. Breast Cancer is the most common cancer in women other than skin cancer.

Due to the ramifications of treatment, exercise is a modality that can be used to facilitate recovery, return to function, and ongoing prevention. Numerous studies have demonstrated that exercise can improve quality of life, reduce side effects of treatment, and improve strength and endurance. However, it is essential that health-fitness professionals understand the various treatments that survivors undergo to provide safe and effective exercise programs. It is important to understand where in the recovery continuum the fitness professional can start with exercise programming minimizing risk of potential exercise side effects and complications.

Following are 5 things to know about exercise for clients with breast cancer.  It is important to understand how to safely and effectively work with the client through recovery, through treatment (chemotherapy and radiation), and then into the prevention and survival phase.  Specialized continuing education will qualify you to work with this growing group of clients who can greatly benefit from the care and expertise of a trained exercise professional.

1. There are two types of local treatments for breast cancer: surgery and radiation. Surgery can be radical (involving breast tissue, and surrounding nerves and muscles) or relatively non-invasive (such as lumpectomy), but typically involves the lymphatic system with removal of lymph nodes.  Knowledge of treatment is important for exercise for recovery.

2. Systemic treatments include chemotherapy and hormonal treatments (typically via medication) which affect all systems in the body, not just the surrounding tissue. Exercise can help with the side effects of systemic treatment, but must be adjusted or suspended for certain signs and symptoms which may require referral back to the health care provider.

3. One of the primary goals for breast cancer recovery should be to restore range of motion to the chest and shoulder including flexion, abduction, and internal/external rotation. The muscles most affected are the pectoralis major, serratus anterior, and the rotator cuff. Typically a client will work with a therapist initially to re-establish range of motion, and then can be referred to a fitness professional who will work with the client to retain range of motion and improve strength.

4. If your client has lymphedema or is at risk for lymphedema, research indicates that order of exercises is important. Use a proximal to distal exercise sequence designed to encourage lymphatic flow in alternative pathways. Muscles are contracted in the abdomen, chest, and shoulders and then to the arm to reduce fluid in the arm.

5. It is important to have physician’s clearance before starting an exercise program with someone who is recovering from or has a history of breast cancer. In recovery, it is good to make contact with the therapist that is on the health care team to work together for the client in the continuum of care.

Fitness Learning Systems (an IACET accredited continuing education provider) offers a Breast Cancer Recovery and Prevention Specialist Certificate Program for 12 hours of specialized continuing education. Expand your knowledge and specialize in order to expand your expertise and income.
Special Offer: The Holland Foundation, Inc (a family related breast cancer foundation) is sponsoring 5 people who want to receive this credential with a $50.00 discount. To use this sponsorship, be one to the first 5 people to use the coupon code “HOLLAND” at check out. The Breast Cancer Recovery and Prevention Specialist Certificate Program is recommended by the American Breast Cancer Foundation.