Abstract
BACKGROUND: High-intensity resistance training induces structural and functional adaptations in skeletal muscle, yet its impact on cardiac remodeling remains debated. This study aimed to investigate the longitudinal biventricular cardiac response to a 20-week high-intensity resistance training program in previously untrained, healthy males and examine the association between muscle strength gains and cardiac remodeling. METHODS: Twenty-seven male volunteers (aged 18-40 years) participated in a high-intensity resistance training program for 20 weeks. Assessments at baseline, 12 weeks, and 20 weeks included resting blood pressure, electrocardiogram (ECG), three-dimensional transthoracic echocardiography (3DTTE), cardiopulmonary exercise testing ([Formula: see text]O(2peak)), isokinetic dynamometry for muscle strength, and actimetry recordings. Time effects were analyzed using one-way repeated measures ANOVA (P < 0.05). RESULTS: Twenty-two participants completed the study. Resistance training led to significant reductions in arterial systolic and diastolic blood pressure and heart rate. After 20 weeks of training, 3DTTE showed a significant increase in left ventricular (LV) mass (120.1 ± 15.4 g vs. 133.7 ± 16.3 g, p < 0.001), without inducing LV hypertrophy. Balanced increases were observed in LV end-diastolic volume (146.4 ± 18.9 ml vs. 157.9 ± 19.6 ml, p < 0.001) and right ventricular (RV) end-diastolic volume (119 ± 19.4 ml vs. 129.2 ± 21.6 ml, p < 0.001). LV and RV systolic and diastolic function remained unchanged. There were no changes in [Formula: see text]O(2peak) or daily activity levels. Maximal muscle strength in the quadriceps, hamstrings, triceps, and biceps was significantly correlated with LV and RV end-diastolic volumes and LV mass (p ≤ 0.001). CONCLUSION: The resistance training program resulted in significant and rapid muscle strength gains and reduced blood pressure. Cardiac adaptations, including moderate biventricular dilatation, were observed without changes in cardiac function or [Formula: see text]O(2peak) and were associated with muscle strength gains. Our study highlights that intensive resistance training in novice male resistance trainers induces an adaptive cardiac response, reflecting a physiological adaptation linked to enhanced muscle performance. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT04187170.