BACKGROUND: Over the season, competitive swimmers experience a progressive imbalance in rotator cuff strength, predisposing them to a significant risk factor for a swimmer's shoulder injury. OBJECTIVES: Verify the effectiveness of two 12-week preventive programs on the shoulder rotators' peak torque and conventional/functional ratios. DESIGN: A care provider- and participant-blinded, parallel, randomized controlled trial with three groups. PARTICIPANTS: Competitive swimmers aged 16 to 35 years with no prior clinical issues related to their shoulders. INTERVENTIONS: Twice a week, over 12 weeks, the two experimental groups performed five exercises where the only difference was executing the program with weights or elastic bands, and the control group performed a sham intervention. MAIN OUTCOME MEASURES: The concentric and eccentric peak torque of the internal and external rotators of the dominant shoulder were assessed before and after the intervention using an isokinetic dynamometer Biodex System 3, at 60°/s, 120°/s, and 180°/s. RESULTS: Among the experimental groups, only one test indicated a reduction ( CONCLUSIONS: Implementing a 12-week preventive program minimizes the progressive shoulder rotational imbalance over the season in competitive swimmers. CLINICAL TRIAL REGISTRATION NUMBER: NCT06552585.