External Load Across Menstrual Cycle Phases in Spanish Professional Female Soccer Players: An Observational Study Using App-Based Cycle Tracking

Monitoring training load in professional soccer should account for sex-specific physiological rhythms, including menstrual cycle fluctuations. Although app-based tracking tools provide a non-invasive solution for estimating cycle phases, their relationship with performance metrics remains unclear. This study investigates whether external training load varies across menstrual cycle phases estimated via app-based tracking in professional female soccer players during pre-season and early competition. Thirty-one professional female soccer players (age: 23.29 ± 4.27 years) from two Spanish teams participated in this prospective, longitudinal, and observational study. Global Positioning System (GPS)-derived external load was recorded daily during all training sessions over five weeks of pre-season and early competition. Menstrual cycle phases were estimated using the FitrWoman app and classified into four physiological phases. Phase-based differences were analyzed using one-way ANOVA with post hoc tests. The follicular to ovulation phase consistently showed the highest values in total distance (TD), maximum velocity (Vmax), and walking distance compared to the other phases (all p ≤ 0.002). No significant effects were observed in the remaining GPS-derived variables. Overall, menstrual cycle phase may influence specific aspects of training load, and app-based monitoring may offer a feasible strategy to contextualize performance data in elite environments.