Range of Motion, Humeral Retroversion and Rotator Cuff (RC) Muscle Strength of the Shoulder in Overhead Athletes

Overview

* Shoulder pain and dysfunction are common problems in overhead sports, due to extreme ranges of motion and repetitive loading. Predisposing factors include inadequate range of motion (ROM), such as a reduction in total ROM or a shift of balance between internal and external rotation. Such a shift may be the result of soft tissue adaptations to the activity demands, or reflect a structural outcome of Humeral retroversion. A shift in the range of motion may be detrimental to the rotator muscle function, which may create another risk factor for shoulder injury. * The purpose of this study is to document shoulder range of motion, humeral retroversion, rotator muscle strength and fatigue in several groups of overhead athletes undergoing a routine pre season screening once a year, and investigate the interaction between those factors in the different groups.

At the commencement of training season athletes will receive a detailed explanation and sign an informed concent form. * Upon enrollment each athlete will fill a personal questionnaire, including injury history. This is done in accordance with a regular screening performed on those teams. * ROM will be measured in the supine position, as described in detail in the work of Almeida et al, J shoulder Elbow Surg 2013, 22 , 602-607. * Following the ROM measurement, assessment of Humeral retroversion via Ultrasound will be carried out, as described and validated by Myers J et al, Am J Sports Med, 2012, 40: 1155-1160. * Strength testing will be then commenced. A structured warm up procedure consisting of 2 sets of rotation exercises using Theraband will be carried out. Following this a pre - set order of testing consisting of isometric- isokinetic concentric, isokinetic eccentric testing will be performed. This order was chosen in order to allow maximal physiologic preparation and safety during testing. The first side to be tested will be determined randomly. * Isometric testing will be carried out in the seated, 90/90 position with respect to shoulder and elbow. This position was chosen to reflect as closely as possible the functional range of the dominant shoulder during athletic activity. 3 Contractions of 3 second each, external rotation will be performed, followed by 3 contractions of 3 seconds each into internal rotation. Both will be held against a stationary pad. * Isokinetic testing will commence following a familiarization procedure, with subject positioned according to manufacture's manual and the protocol described by Zanca et al, J Sports Sciences 2011,29 (15):1603-1611. * Two sets will be performed concentrically, at 60 degrees/second and at 180 deg/second. Eccentric testing will consist of one set utilizing the slow velocity of 60 degrees/sec. * Outcome measures will consist of total range of motion (TROM), difference in internal rotation (GIRD), external rotation gain (ERG), Humeral retroversion (HRT)- all measured in degrees. Strength measurement will consisit of maximal isometric strength (Newton), isokinetic peak torque for each direction (Newton/Meter) and agonist:antagonist muscle ratios- concentric, eccentric and dynamic control ratio ( Eccentric external rotation/concentric internal rotation).