Running Economy After a Low‐ and High‐Intensity Training Session in Naturally Menstruating Endurance‐Trained Female Athletes: The FENDURA Project

The ability to maintain running economy is generally evaluated during a long continuous exercise bouts, and it is unclear whether the menstrual cycle phase acts as a confounder. The first aim of this study was to evaluate the ability to maintain running economy during typical 1‐h low‐ (LIT) and high‐intensity training (HIT) sessions in female athletes. The second aim was to investigate whether menstrual cycle phase affected the ability to maintain running economy. Naturally menstruating endurance‐trained females performed three LIT (n = 16) (45%–55% of the maximal velocity achieved during the maximal incremental test) and/or three HIT sessions (n = 17) (5 × 4 min at 80% of the maximal velocity achieved during the maximal incremental test) during three distinct menstrual cycle phases: early follicular, ovulatory, and mid luteal. Running economy was determined before and after each session. Running economy, expressed as energy cost (before: 1.34; after: 1.34 kcal/kg/km, p = 0.797) and oxygen cost (before: 272, after: 273 mL/kg/min, p = 0.348), was not significantly different before versus after the LIT session. Energy cost (before 1.33; after: 1.34 kcal/kg/km, p = 0.130) was not significantly different before versus after the HIT session, but oxygen cost (before: 269; after: 274 mL/kg/km, p < 0.003) was slightly higher after the session. Menstrual cycle phase did not confound the ability to maintain running economy. Running economy can be maintained during a typical 1‐h LIT session. The ability to maintain running economy during a typical HIT session depends on the expression used; energy cost was unaffected, while oxygen cost may be slightly increased after HIT sessions.