This randomized controlled trial investigated the effects of a 10-week intervention incorporating imagery and breathing exercises on swimming performance, mental toughness, and cardiac coherence in adolescent swimmers. Nineteen licensed swimmers (aged 13–18 years) were randomly assigned to either an experimental group (n = 9), receiving daily 15-min imagery and breathing sessions in addition to regular training, or a control group (n = 10), receiving standard training alone. Pre- and post-intervention assessments included 200-m freestyle performance, the Sports Mental Toughness Questionnaire (SMTQ), and cardiac coherence measured via the Inner Balance HeartMath device. Repeated measures ANOVA revealed significant improvements in cardiac coherence (p = 0.008, η² = 0.349) and mental toughness (p = 0.003, η² = 0.414) in the intervention group. Although swimming performance improved in both groups (p < 0.001), the group × time interaction was not significant (p = 0.529), suggesting that improvements may reflect practice effects rather than intervention-specific benefits. Due to the small sample size (n = 19), the study is best considered a pilot, with findings warranting further investigation in larger, stratified samples to enhance generalizability. These results highlight the potential psychological benefits of imagery and breathing exercises in youth athletes and support their integration into training protocols, with future studies needed to confirm performance effects.
Girginer et al. (Tue,) studied this question.