Kebaetse M, McClure P, Pratt NA. Thoracic Position Effect on Shoulder Range of Motion, Strength, and Three-Dimensional Kinematics. Arch Phys Med Rehabil, 1999; 80:945-50.
The objective of this study was to determine the effects of thoracic spine posture in the sagittal plane on shoulder function. Healthy subjects were tested in a sitting position with the thoracic spine erect and slouched, thereby mimicking the effects of postural kyphosis. The motion tested was shoulder abduction. Isometric strength tests were gathered with the arm by the side (0 degrees) and horizontal (90 degrees of abduction). The authors found that the scapula kinematics were significantly different in the slouched posture. Compared to the erect position, strength at 90 degrees decreased 16 percent in the slouched position and the maximum abduction range of motion was reduced by a mean of 23.9 degrees.
Based on these results, the importance of thoracic spine posture to workers who sit is obvious. As movement practitioners, the effects of thoracic kyphosis on function become apparent. It would not be hard to envision the development of shoulder impingement during sitting activities. Cervical and lumbar symptoms often result from a thoracic spine that is excessively flexed. In addition, these postural positions (and effects) often persist during upright activities when reaching overhead during any number of sports. But most of us would admit that telling our patients / clients to sit up straight creates the desired postural correction for only a few minutes or seconds.
Practitioners of Applied Functional Science® will apply the Principles-Strategies-Techniques (PST) Process to create programs to address this postural problem. The Principles of 3D, Driven, Load to Explode, and Success provide Strategies that provide for logical exercise prescription and progressions. The desired motion / position is less flexion (more extension) in the thoracic spine. But based on Load to Explode, the initiating movement would be flexion. However, since sagittal plane motion is the problem, can the Principle of 3D be used to drive motion into the other more successful planes (frontal and transverse)? Should we drive the motion with the trunk, or can the use of arm Drivers provide us with a better Strategy?
Here is one example of a program to address the problem through subconscious activation of muscle via the proprioceptors: Using a single arm / hand, reach down to the side in the frontal plane. This loads the muscles that will create the explode. As the explode becomes more dynamic, the lateral flexion that is created by the abducting arm will begin to initiate thoracic extension as part of the movement. Now, alternate arms to work both sides. Then the direction of the reaching hand during the load is moved forward away from the frontal plane. This adds sagittal plane motion to the load, which increases the thoracic extension during the load. With continued success the reaching target is moved more anterior thereby adding sagittal (and transverse) plane motion.
The next Strategy might be to limit the loading reach distance, while emphasizing (with a target) the exploding elevation of the arm. Also, when the trunk is in an improved postural position of extension, isometric loading of the arm will increase the strength of the trunk muscles required to maintain this position. Speed. Load, and Duration from the 10 Observational Essentials from the Certification in Applied Functional Science® (CAFS), can be used to individualize the program and maximize success. Find out more here: https://www.grayinstitute.com/courses/cafs.