PHASE-SPECIFIC TRAINING IN EUMENORRHEIC WOMEN: THE ROLE OF MENSTRUAL CYCLE HORMONAL VARIABILITY IN PERFORMANCE AND ADAPTATION: A LITERATURE REVIEW

Background: The menstrual cycle is a fundamental physiological rhythm in eumenorrheic women, driven by fluctuations in estrogen and progesterone. While these hormones influence substrate metabolism and thermoregulation, their actual impact on athletic performance remains debated. Aim: This narrative review aims to evaluate the effects of menstrual cycle phases on acute exercise performance and chronic training adaptations, and to provide evidence-based practical recommendations. Materials and Methods: A comprehensive literature search was conducted across PubMed, Google Scholar, and Scopus databases, covering original research and systematic reviews published between 2005 and 2025. Analysis focused on eumenorrheic athletes with a particular emphasis on studies utilizing biochemical phase verification. Results: Aerobic capacity (VO2max) and running economy remain stable across the cycle. While follicular-phase resistance training may offer superior strength gains in some cohorts, the broader evidence is inconsistent. A significant disconnect exists between physiological capacity and subjective perception, with athletes reporting performance decrements during the late luteal phase due to cycle-related symptoms. Conclusions: Current evidence does not support the universal application of rigid, phase-based training models for eumenorrheic athletes. The high inter-individual variability in cycle characteristics and symptom severity suggests that a generalized approach is insufficient. Instead, practitioners are encouraged to adopt an individualized "symptom-based" monitoring strategy, adjusting training loads in response to specific athlete feedback rather than presumed physiological shifts.