The thoracic spine is situated between the cervical spine (neck) and lumbar spine (low back). The primary osteokinematic function (movement of bones) of the thoracic spine is rotation and, to a smaller degree, extension (bending the spine backward) and lateral bending. All strokes in tennis require some degree of rotation and extension. Inadequate mobility of the thoracic spine may have a deleterious effect upon the shoulder and reduction in stroke power output.
Specifically, thoracic spine rotation is imperative for a high velocity serve and shoulder protection. During loading phase, adequate T/S rotation permits optimal muscle recruitment from trunk musculature (oblique’s and erector spinae). As the torso winds-up like a “cork screw” potential energy is absorbed or harnessed by the trunk musculature which is eventually delivered to the shoulder, elbow wrist, hand and ball. Inadequate T/S rotation will lead to a decrease in serve velocity which is commonly compensated by the shoulder to make up for the lose of force. Kibler et al, discovered that a 20% decrease in kinetic energy from the trunk requires a 34% increase in velocity from the upper extremity (shoulder) to achieve the same kinetic energy to the hand. This may negatively impact the integrity of the shoulder rotator cuff and lead to overuse type injuries.
Thoracic Rotation Exercise
Below are excellent drills to improve or maintain your thoracic spine rotation that will keep you hitting with optimal force and prevent overuse type shoulder injuries such as rotator cuff tenindopathies and biceps tendinopathies.
This exercise allows for eccentric oblique activation (muscles lengthening under tension) while the torso slowly rotates away from the ground. followed by a concentric (muscle shortening under tension) oblique muscle activation when returning to the starting position (chest is pointed toward ground).
This variation requires the same movement but opposite muscle activation from the first variation. In this case, while pulling the band upward toward the sky while rotating, the right paraspinals are concentrically
I like this exercise as to provide passive stretch and joint mobility to the spine. Exhale as you bring the lead hand to the ground. Maintain top knee on the ground to ensure relatively pure thoracic spine rotation.
Thoracic Spine Extension
Limited ability to extend the thoracic spine has been reported to be associated with subacromial impingement (anterior shoulder pain). A study involving 525 individuals compared the prevalence of rotator cuff tears across four postural classifications; ideal alignment, kyphotic-lordotic posture, flat-back posture & sway-back posture . This study reported that the prevalence of rotator cuff tears was lowest in the ideal posture at 2.9% & highest in the kyphotic-lordotic posture at 65.8%.
- Kabaets et al found inadequate T/S extension leads to decreased shoulder range of motion, posterior tilting of the scapula with resultant decrease in shoulder girdle muscle force.
- This may result in increased demand on the elbow & shoulder to achieve max external rotation during cocking phase & deleterious to the shoulder & elbow.
- The increase demand on the shoulder to achieved max external rotation may lead to subacromial impingement syndrome (biceps, rotator cuff, bursa), labral tears, medial epicondylalgia & ulnar collateral ligament sprains.
Citation: Yamamoto, A., Takagishi, K., Kobayashi, T., Shitara, H., Ichinose, T., Takasawa, E., … & Osawa, T. (2015). The impact of faulty posture on rotator cuff tears with and without symptoms. Journal of shoulder and elbow surgery, 24(3), 446-452.).
Citation: Kebaetse, M., McClure, P., & Pratt, N. A. (1999). Thoracic position effect on shoulder range of motion, strength, & three-dimensional scapular kinematics. Archives of physical medicine & rehabilitation, 80(8), 945-950.
Furthermore, A study by Miyashita et al examined the shoulder, scapular & thoracic spine contribution to max external rotation of the shoulder during throwing. The results indicated that both the scapula & thoracic spine play a pivotal role in maximum shoulder external rotation. During the late cocking phase of the serve the shoulder is positioned in max external rotation (the racket head is pointed down toward the ground). This phase is critical to allow the player to harness max potential energy of the shoulder internal rotators (subscapularis, pec major, latissimus dorsi). Indaequate thoracic spine extension may lead to compensation from the shoulder and place excessive demand on the medial (inner) aspect of the elbow.
Citation: Miyashita, K., Kobayashi, H., Koshida, S., & Urabe, Y. (2010). Glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation in throwing. The American journal of sports medicine, 38(2), 363-368.
Briefly, the subacromial space is defined by the coracoacromial ligament and acromioclavicular (AC) joint superiorly, the anterior edge and undersurface of the acromion, and the humeral head inferior.
The structures of the Subacromial acromial space that are susceptible to impingement are supraspinatus tendon (1 of 4 rotator cuff muscles), subacromial Bursa, Long head of the biceps tendon, Coracoacromial ligament.
As stated before, lack of thoracic spine extension is commonly observed in individuals who suffer from subacromial impingement.