Hypomobility in Males and Hypermobility in Females are Risk Factors for Shoulder Pain Among Young Swimmers.

CONTEXT: The range of shoulder rotation is associated with shoulder pain in young male and female swimmers. However, the association between shoulder pain and shoulder complex mobility of the scapulothoracic and acromioclavicular joints has not yet been examined. Moreover, shoulder pain occurs more frequently in females than in males, but only a few studies have examined the relationship between shoulder pain and sex as a risk factor. This study aims to determine the association between shoulder complex mobility and shoulder pain in young male and female swimmers. DESIGN: Prospective cohort design. METHODS: The participants were competitive swimmers (n = 76; 37 males and 39 females) with a mean age of 14 years in Japan. The shoulder rotation width, which was the index of shoulder complex mobility, shoulder internal and external rotation range, and middle finger distance of the back-scratch test were measured. An examiner regularly visited the swimming clubs to evaluate the development of shoulder pain and swimming distance. Logistic regression analysis was used to determine the physical characteristics related to the overall development of shoulder pain in both female and male swimmers. The cutoff value was calculated using receiver operating characteristic curves. RESULTS: Sixteen participants, composed of 8 males and 8 females, developed shoulder pain. The overall swimming distance of the male (odds ratio [OR]: 1.0007, P = .01) and female (OR: 1.0018, P = .02) swimmers and the shoulder rotation width of the male (OR: 1.0952, P = .04) and female (OR: 0.888, P = .03) swimmers were identified as risk factors for shoulder pain. The cutoff value for swimming distance was 6000 m. Shoulder rotation width was more than 88 cm in males and <54 cm in females. CONCLUSIONS: Hypomobility and hypermobility of the shoulder complex were identified as risk factors for shoulder pain in male and female swimmers, respectively.

Does scapular dysfunction alter scapular muscles activity and kinematics during swim stroke motion on adolescent swimmers?

Scapular dyskinesis (SD) indicates dysfunction of the scapular muscle activity during the arm elevation, resulting in altered scapular kinematics. This study examined whether SD alters scapular muscle activity and kinematics during swim stroke motion. Seventeen swimmers (mean age: 13 ± 1 years) were divided into SD (n = 8) and control (n = 9) groups. Scapular muscle activity (the upper, middle, and lower trapezius and the serratus anterior muscle) and kinematics data were collected and time-normalised (0-100%) during swim stroke motion by swim-bench on land. Scapular kinematics were calculated for upward rotation, internal rotation, posterior tilt, and arm elevation angles. To compare patterns of muscle activity and kinematics with and without SD, statistical parametric mapping unpaired t-test was used. The scapular upward rotation angle was decreased in SD compared to control in the 0-10% of the swim stroke phase (p = 0.041, t* = 3.018), and the internal rotation angle was increased in 0-15% of the phase (p = 0.033, t* = 2.994). Scapular posterior tilt and muscle activity showed no significant differences. These results suggested that SD altered scapular upward rotation and internal rotation at the initial phase of the swim stroke motion in adolescent swimmers and might potentially provoke a risk of subacromial impingement.

Posterior deltoid shoulder tightness and greater contralateral lower limb muscle strength are associated with swimmers' shoulder pain.

OBJECTIVES: To identify factors associated with shoulder pain in swimmers based on elastic muscle modulus, joint range of motion, and isometric muscle strength. DESIGN: Cohort study. METHODS: Forty-eight competitive swimmers without shoulder pain (age: 18-28 years; men: 29) were followed-up for 6 months. Baseline measurements of the elastic modulus of the pectoralis minor, supraspinatus, infraspinatus, posterior deltoid, and pectoralis minor muscles were obtained using shear wave elastography. Range of motion and isometric strength were measured using a goniometer and a hand-held dynamometer, respectively. A questionnaire was administered weekly for 6 months to determine shoulder pain occurrence. Each item was compared between shoulders with and without pain at baseline. For participants with shoulder pain exceeding 2 weeks, shear wave elastography and range of motion at baseline (pre pain) and during follow-up (post pain) were compared. RESULTS: Of 46 swimmers followed-up for 6 months, 20 reported shoulder pain. 14 swimmers with pain were evaluated twice. Participants with shoulder pain during follow-up had significantly higher posterior deltoid and pectoralis minor stiffness at baseline and high lower extremity isometric muscle strength contralateral to the shoulder with pain compared to those without pain (p < 0.05). Swimmers with pain exceeding 2 weeks exhibited no differences in ultrasound shear wave elastography and range of motion at baseline and after pain onset. CONCLUSIONS: Posterior deltoid and pectoralis minor muscle stiffness, and high isometric lower extremity strength contralateral to the shoulder with pain may be associated with shoulder pain development, thereby indicating the importance of maintaining posterior deltoid and pectoralis minor muscle flexibility during conditioning.