Effect of Biological Maturation on Shoulder Rotator Strength and Performance After a 6-Week Summer Break in Young...

Santos, CC, Marinho, DA, and Costa, MJ. Effect of biological maturation on shoulder rotator strength and performance after a 6-week summer break in young male swimmers. J Strength Cond Res XX(X): 000-000, 2026-This study aimed to analyze the effects of biological maturation on shoulder rotator strength and performance after a 6-week summer break in young male competitive swimmers. Twelve young swimmers were divided into pre- and mid-peak height velocity (PHV) groups. Anthropometric variables (body mass, stature, and arm span) and dryland shoulder rotator cuff strength (internal rotation; external rotation, strength balance; internal rotation/external rotation ratio) of both limbs were measured in pre- and post-test (6-week apart), alongside 25 m front crawl performance (time, T25; speed, s25) and kinematics (stroke rate; stroke length; stroke index, SI). ANOVA (level of significance p ≤ 0.05) revealed between-group (maturity offset [MO]) effects for body mass, stature, arm span, T25, s25, stroke length, and SI, indicating that mid-PHV swimmers had larger anthropometrics, strength, and stroke efficiency. Time effects were observed only for SI, while no interaction MO*time was observed. A natural growth was experienced by both MO groups, being more evident in pre-PHV swimmers. Mid-PHV swimmers showed improvements in shoulder rotator strength balance, whereas pre-PHV swimmers showed greater muscular imbalances after the summer break. Performance and kinematic variables remained stable or even slightly improved. A 6-week summer break did not impair shoulder rotator strength or swimming performance in either MO group. Thus, the interpretation of (de)training effects according to each swimmer's MO could become standard practice among swimming coaches.