Menstrual cycle hormonal fluctuations and their associations with athletic performance and injury susceptibility in female athletes.

BACKGROUND: The menstrual cycle (MC) is characterized by periodic fluctuations in estradiol and progesterone that may influence exercise metabolism, neuromuscular function, connective-tissue properties, menstrual symptom burden, recovery, and musculoskeletal injury susceptibility in female athletes. However, inconsistent findings and substantial inter- and intraindividual variability have prevented the development of universally applicable practical guidance. OBJECTIVE: This narrative review aimed to synthesize current evidence on the associations of MC-related hormonal fluctuations with athletic performance and injury susceptibility; examine the underlying physiological, biomechanical, and psychological mechanisms; and evaluate the practical implications for training, nutrition, recovery, and injury prevention. MAIN FINDINGS: The available evidence indicates that associations between the MC phase and objective performance outcomes are generally weak, variable, task-specific, and highly individual. Some studies have reported phase-related differences in selected measures of muscle strength, explosive performance, endurance strain, or training adaptation, whereas other studies have found no meaningful differences. Therefore, no MC phase can currently be considered universally advantageous or disadvantageous for athletic performance. Estradiol, progesterone, and relaxin provide biologically plausible pathways through which connective tissue metabolism, joint laxity, neural excitability, sensorimotor processing, and muscle-activation strategies might be modified. However, much of the supporting evidence is derived from experimental laboratory surrogate outcomes rather than prospectively recorded clinical injury data. Observational evidence linking distinct menstrual phases to anterior cruciate ligament tears, muscle strains, and other musculoskeletal injuries remains limited, heterogeneous, and unable to confirm direct causal links. LIMITATIONS: Interpretation of the evidence is constrained by small sample sizes; inaccurate or inconsistent phase classification; limited hormonal verification; inadequate control of training load; energy availability, sleep, and hormonal contraceptive use; and substantial between- and within-individual variability. PRACTICAL IMPLICATIONS: Current evidence does not support rigid or universally applied phase-based training rules, nor arbitrary risk/performance labeling of MC phases. MC status should be considered contextual information rather than an independent basis for training prescription. Training and injury-prevention decisions should be guided primarily by repeated individual monitoring of menstrual symptoms, perceived readiness, recovery, nutritional intake, objective performance, training load, environmental stressors, and previous injury. Established neuromuscular injury-prevention and workload-management strategies should be implemented throughout the cycle rather than restricted to presumed vulnerable phases.