Longitudinal Selected Predictors Influencing 50-Metre Breaststroke Performance in Pre-Adolescent Non-Elite Female Swimmers

Background: Breaststroke performance in young swimmers is influenced by a complex interaction of anthropometric, physiological, and technical factors. However, existing studies predominantly focus on pre-selected or elite youth swimmers, limiting insight into performance development in non-elite populations without early selection bias. Purpose: This study aimed to identify key predictors of 50-m breaststroke performance and to examine longitudinal changes in selected characteristics in pre-adolescent, non-elite female swimmers. Methods: Fourteen female swimmers (baseline biological age: 10.52 ± 0.37 years) who entered swimming training without prior anthropometric or physiological selection were followed over three consecutive years. Measurements were collected at six time points and included anthropometric dimensions, body composition, aerobic and anaerobic capacity, respiratory volumes, and 50-m breaststroke performance. This investigation was a prospective longitudinal cohort study. Data were analysed using generalised estimating equations. Results: The correlation-filtered model explained 76% of the variance in 50-m breaststroke time. Chest depth (B = −0.16, p = 0.03), foot length (B = −0.17, p = 0.04), foot width (B = 0.30, p < 0.001), and shoulder width (B = −0.07, p = 0.04) emerged as significant anthropometric predictors. Maximal oxygen uptake also showed a significant association with performance (B = −0.33, p = 0.02). Conclusions: In pre-adolescent, non-elite female swimmers, selected anthropometric characteristics—particularly trunk dimensions and foot morphology—are associated with short-distance breaststroke performance. Aerobic capacity appears to play an indirect, supportive role. These findings highlight the importance of longitudinal monitoring without early selection and support a development-oriented approach to youth swimming training.