Comparison of the Physical Fitness Levels between Premenarcheal and Postmenarcheal Adolescents

Research findings on understanding the critical impact of biological maturation on physical performance through research findings will enable coaches and physical educators to group adolescent athletes based on their biological maturity levels rather than chronological age. This approach will allow them to design fairer, safer, and more effective training programs by identifying potential risks, such as losses in strength and speed observed during the post-menarche period, and developing strength and injury prevention strategies specific to this phase. Therefore, this study aims to investigate the effect of menarche on the physical fitness levels of adolescent female groups. In the study, pre-tests were administered to 26 sedentary pre-pubertal female students of different ages, measuring body weight, height, BMI, flexibility, vertical jump, handgrip strength, backward medicine ball throw, agility, and sprint speed. Nine months later, the physical fitness tests were repeated for the same participants, who were divided into two groups: those who had not yet experienced menarche (premenarcheal), with a mean age of 151.77 months (12.65 years), and those who had started menstruating (postmenarcheal), with a mean age of 166.92 months (13.91 years). Data analysis included an independent t-test to compare the two groups during pre- and post-tests and a paired sample t-test to determine the 9-month changes in physical fitness components within each group. The findings of this study reveal that menarche has complex and multifaceted effects on the physical fitness parameters of adolescent girls. During the pre- and post-tests, only the mean sprint speed of the younger premenarcheal group differed significantly from that of the older postmenarcheal group. Over the nine-month period, the premenarcheal group showed moderate effect sizes in height and small effect sizes in body weight and BMI, whereas the postmenarcheal group exhibited small effect sizes in height and body weight and a large effect size in mean sprint speed. In the younger group, non-significant increases were observed in flexibility, vertical jump, and medicine ball throw, while non-significant decreases were noted in right and left handgrip strength. In the older postmenarcheal group, non-significant increases were found in BMI and flexibility, whereas non-significant decreases were observed in right and left handgrip strength and agility. The results highlight the critical relationship between biological maturity level and physical performance, emphasizing the necessity of planning training programs based on biological maturity rather than chronological age. Specifically, the declines in handgrip strength and variability in sprint performance observed during the post-menarche period point to risks unique to this transitional phase. In light of these findings, the most important practical implication for coaches and physical education specialists is that evaluating early- and late-maturing individuals within the same groups may negatively affect performance and potentially increase the risk of injury. In conclusion, this study provides a significant scientific foundation for monitoring the physical fitness levels of girls, especially during the pre-menarche period, and for developing targeted strengthening, body composition monitoring, and injury prevention strategies specific to this phase.