Shoulder structures and strength in competitive preadolescent swimmers: A longitudinal ultrasonographic study.

BACKGROUND

Repetitive shoulder movements during competitive training may cause changes in the strength of periarticular shoulder structures in preadolescent swimmers.

OBJECTIVE

To prospectively determine the effects of training on shoulder periarticular structures and muscle strength in preadolescent swimmers.

DESIGN

Prospective cohort study.

SETTING

Community-based natatorium.

PARTICIPANTS

Twenty-four preadolescent swimmers aged 10-12 years.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Measurements were repeated in three periods as preseason, midseason, and postseason. Ultrasonographic measurements (supraspinatus tendon thickness, humeral head cartilage thickness, deltoid muscle thickness, and acromiohumeral distance) were performed using a portable device and a linear probe. Shoulder (flexion, extension, abduction, internal and external rotation) and back (serratus anterior, lower, and middle trapezius) isometric muscle strength were measured with a handheld dynamometer.

RESULTS

Supraspinatus tendon thickness and acromiohumeral distance were similar in all periods (all p > .05); however, deltoid muscle and humeral head cartilage thicknesses increased throughout the season (p = .002, p = .008, respectively). Likewise, whereas shoulder muscle strength increased (all p < .05), back muscle strength was similar in all periods (all p > .05).

CONCLUSIONS

In preadolescent swimmers, acromiohumeral distance and supraspinatus tendon thickness seem to not change; but humeral head cartilage and deltoid muscle thicknesses as well as shoulder muscle strength increase throughout the season.