Research Review By Patrick Ward©

Date Posted:

August 2010

Study Title:

The Relationship Between Forward Scapular Posture and Posterior Shoulder Tightness Among Baseball Players

Authors:

Laudner KG, Moline MT, Meister K

Author's Affiliations:

Biomechanics Laboratory, School of Kinesiology and Recreation, Illinois State University, Normal, Illinois, Casper College, Casper, Wyoming, and Texas Metroplex Institute for Sports Medicine and Orthopedics, Arlington, Texas.

Publication Information:

American Journal of Sports Medicine 2010 (in press)

Background Information:

Poor scapular position and control, referred to as scapular dyskinesis, has been one of the factors implicated in shoulder pathologies like subacromial impingement and SLAP (superior labral anterior posterior) lesions in baseball players and other overhead athletes (1-4). Kibler (1998) states, “The scapula must rotate in the cocking and acceleration phases to clear the acromion from the rotator cuff to decrease impingement and coracoacromial arch compression.” (1).

Burkhart et al (2003) have described the position of the scapula in a pathological shoulder as SICK – Scapula malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement (5). This position can be seen visually in the athlete as their scapula on the affected side (throwing shoulder) will appear to be “dropped” and the inferior border, when viewed from the back, will appear very prominent. From the front, the shoulder appears protracted and again lower than the opposite shoulder (5).

Tightness of the pectoralis minor has been one of the muscles implicated in this position of the scapula as its attachments on the coracoid process and the 3rd-5th ribs pull the scapula into greater protraction. Burkart et al (2003) state that the attachment of pectoralis minor on the coracoid may be tender upon palpation, and that those with SICK scapula will often complain of shoulder or arm pain that typically has an insidious onset (5).

Given the correlation between scapular dyskinesis and shoulder injury, researchers have attempted to develop better strategies for screening and assessing athletes to ensure that appropriate measures are taken to help avoid injury. This study sought to add to that body of research by further suggesting a relationship between posterior shoulder tightness and forward scapular position.

Pertinent Results:

  • The dominant shoulder of both pitchers and position players were significantly forward compared to the nondominant shoulder.
  • There is a relationship between posterior shoulder tightness, as measured by glenohumeral adduction, and forward scapular positioning.
  • There was a negative relationship between glenohumeral adduction and forward scapular position. Those with greater posterior shoulder tightness had greater forward scapular position than those with less posterior shoulder tightness.
  • No significant relationships were found between scapular posture and glenohumeral internal or external rotation.
  • Differences in internal and external glenohumeral rotation were noted between dominant and nondominant shoulders, with a tendency towards greater external rotation and decreased internal rotation in the dominant shoulder. However, the total arc of motion between the two arms was similar. These findings are consistent with other findings on baseball athletes (6).

Clinical Application & Conclusions:

Trying to minimize the risk of injury should be a goal of any good strength and conditioning program. Shoulder injuries are common among overhead athletes (1-5) and having a comprehensive assessment before initiating a strength and conditioning program is essential to ruling out potential risk factors that may lead the athletes to injury during competition or practice (1, 7-8).

This current study evaluated four tests to draw a correlation between forward scapular position and posterior shoulder tightness. For strength coaches working with overhead athletes, it is important to consider these tests and factors when assessing your clients. While the tests in this study were passive, it should be noted that active tests/assessments should be utilized to gain a further understanding of the athletes’ capacity to move and function. Further, these assessments should not be limited to the shoulder, as the scapula and shoulder function in a chain reaction with the entire body to transfer force from the ground to the arm.

Kibler (1998) states, “The scapula is pivotal in transferring the large forces and high energy from the major source for force and energy--the legs, back, and trunk--to the actual delivery mechanism of the energy and force--the arm and the hand.”(1). It is important to keep the entire body in mind during our assessment process.

In a paper on the kinetic chain relationship to elbow dysfunctions, Kibler and Sciascia (2004) make the point that when evaluating athletes with elbow problems to take into consideration other factors that affect loading such as the shoulders, trunk, and legs (8).

These statements are in agreement with McMullen and Uhl (2003) who suggest a kinetic chain approach to rehabilitation of shoulder by integrating the legs and trunk (7). While both of these papers are dealing with athletes in a rehabilitation setting, as strength coaches we can learn a lot from these concepts.

Oftentimes as strength coaches we are part of a comprehensive medical team that includes physicians, athletic trainers, physical therapists, and chiropractic physicians. By understanding our role and the goals of the individual athlete’s rehabilitation we can develop strength and conditioning programs that are appropriate for a variety of settings and that assist the athlete in a safe and healthy return to sport.

Additionally, from these concepts offered in these papers we can better develop comprehensive strength training programs for non-injured athletes that focus on integrating whole body movements and not just single joint movements aimed at stabilizing muscles, such as the rotator cuff musculature, which are muscles of timing and firing, not necessarily of strength (9).

This current paper offers us one piece in a very large puzzle of athletic assessment and development. Static postures and ranges of motion play a role in the evaluation of athletes prior to initiating a strength and conditioning program. However, the strength coach should keep in mind that proper movement, control, and strength are also important qualities to assess to gain a full appreciation for the athletes functional abilities.

A comprehensive assessment for overhead athletes should include some specific range of motion assessments – as utilized in this paper – as well as an overall assessment of the entire body, especially integrating movement patterns that include the trunk and legs.

Study Methods:

Subjects:
  • 20 professional baseball pitchers
  • 20 professional baseball position players
  • Subjects had no recent history (past 2 years) of shoulder or elbow injury
  • Subjects had no previous upper extremity surgery
  • The study was conducted during spring training with one single Major League Baseball team
Procedures:
  • Subjects volunteered to be tested during their initial physical exam during spring training.
  • Examiners were blinded to the dominant and nondominant arms of the athletes.
  • Four measurements were taken: forward scapular posture, glenohumeral horizontal adduction range of motion, glenohumeral internal range of motion, and glenohumeral external range of motion.
Explanation of testing procedures:
  • Forward scapular posture was measured using the double square method. Subjects stand with their back against the wall and one of the squares is placed against the wall over the shoulder to be tested and the other square is extended along a twelve inch ruler until it makes contact with the anterior tip of the acromion process. This distance is measured to determine the amount of forward scapular posture. The measurement of the nondominant arm was subtracted by the measurement of the dominant arm to determine the bilateral difference.
  • To assess posterior shoulder tightness, glenohumeral horizontal adduction in the supine position was utilized. Subjects lied supine on a treatment table. The test shoulder was positioned in 90° of shoulder flexion and the lateral border of the scapula was stabilized with the examiners thumb by applying a posterior directed force. Holding the forearm slightly distal to the elbow, which was flexed to 90°, the examiner moved the arm into horizontal adduction. Once the end range of motion was reached, a second tester took a measurement using a digital inclinometer and measuring the end position of the humerus with the perpendicular plane of the treatment table (the start position of the test at 0° of horizontal adduction).
  • Glenohumeral internal and external rotation was assessed with the subjects lying in supine with the shoulder and elbow in 90° of abduction and flexion. The examiner supported the humerus to ensure it stayed on level plane with the acromion process and to stabilize the scapula and minimize motion at the scapulothoracic joint. A digital inclinometer was used to assess the angle of the ulna during external or internal rotation in relationship to the perpendicular plane of the treatment table.

Study Strengths / Weaknesses:

  • Subjects in this study were pain free and uninjured, so extrapolating these results to pathological athletes may be difficult.
  • This study only took into account passive range of motion tests. Movement assessment and the ability to control the shoulder and scapula in dynamic situations when the muscular system is active would be an added value in understanding the full spectrum of how the scapula and shoulder work together in an athletic population.
  • This study evaluated only professional athletes and may not be representative of adolescent athletes.
  • The results of the passive range of motion tests in this study support the results of similar studies in this population. As a strength coach working with overhead athletes, the similarities confirmed between several research groups should indicate that shoulder and scapular position is something we should consider in our overall assessment of these athletes prior to initiating a strength and conditioning program.

Additional References:

  1. Kibler WB. Current Concepts: The Role of The Scapula in Athletic Shoulder Function. American Journal of Sports Medicine 1998; 26(2):325-337.
  2. Forthomme B, Crielaard JM, Croisier JL. Scapular Positioning In Athletes Shoulder. Sports Med 2008; 38(5): 369-386.
  3. Heyworth BE, Williams RJ. Internal Impingement of the Shoulder. American Journal of Sports Medicine 2009 May; 37(5): 1024-37.
  4. Nijis J. Roussel N, Strufy F, Mottram S, Meussen R. Clinical Assessment of Scapular Positioning Without Shoulder Pain: State of the Art. J of Manipulative and Physiological Therapeutics 2007; 30(1): 69-75.
  5. Burkhart SS, Morgan CD, Kibler WB. The Disabled Throwing Shoulder: Spectrum of Pathology Part III: The SICK Scapula, Scapular Dyskinesis, the Kinetic Chain, and Rehabilitation. The Journal of Arthorscopic and Related Surgery 2003; 19(6): 641-661.
  6. Reagan KM, Meister K, Horodyski MB, Werner DW, Carruthers C, Wilk K. Humeral retroversion and its relationship to glenohumeral rotation in the shoulder of college baseball players. Am J Sports Med. 2002;30:354-360.
  7. McMullen J, Uhl TL. A Kinetic Chain Approach For Shoulder Rehabilitation. J Athletic Training 2003; 35(3): 329-337.
  8. Kibler WB, Sciascia A. Kinetic Chain Contribution to Elbow Function and Dysfunction in Sports. Clinical Sports Medicine 2004; 23: 545-552.
  9. Cook G, Burton L, Kiesel K, Rose G, Bryant M. Movement – Functional Movement Systems: Screening, Assessment, and Corrective Strategies. On Target Publications. Santa Cruz, Ca. 2010.