Menarche as Maturational Factor in Young Swimmers' Development of Morphological, Physical and Performance Characteristics over a Year of Training.

PURPOSE At the age of menarche, there is a significant increase in the secretion of sex hormones, affecting physical and morphological growth. This study aimed to investigate the impact of menarche on the development of body dimensions, fitness level, technical skills and performance in pubertal female swimmers over one year of training. METHODS Nineteen young swimmers within the same age group (11-12 years) were assessed in two consecutive years. Participants were allocated into two groups (Menarche and Pre-menarche) based on the presence of menarche in the transition from the 1st to the 2nd year. Anthropometric measures, physical fitness (countermovement jump and handgrip), skill tests (glide and 10 m underwater from start and push) and specific performance tests (50, 100, and 200 m) were evaluated. RESULTS Menarche-based differences were identified in handgrip strength, 10 m underwater from push, and sprint performance in the 2nd year (P < 0.05), with menarcheal girls showing greater improvement in these attributes throughout the year. In contrast, premenarcheal swimmers exhibited greater increases in body dimensions (stature, body mass, foot and hand lengths) up to 9.5% and improved performance in the 200 m, reducing the significant differences compared to menarcheal girls in the 2nd year. Muscular strength, hand length, and 10 m underwater performance were significantly associated with short-distance performance, especially in menarcheal girls (r > 0.59), while maturity and training were more related to 200 m performance (P < 0.05). CONCLUSIONS These findings highlight the different timing of improvement in female swimmers' attributes based on menarche. Along with the age at peak height velocity (APHV), the age of menarche might be a valuable tool for monitoring and adapting training and talent identification processes.