Menstrual cycle phase and running economy

To further elucidate the relationship between RE and menstrual cycle phase, eight eumenorrheic moderately-trained female runners were studied throughout their menstrual cycles, which were divided into five phases: early follicular (EF), late follicular (LF), early luteal (EL), mid-luteal (ML), and late luteal (LL). Subjects were studied at rest and while running at speeds initially corresponding to 55% and 80% maximal oxygen consumption (VO2max). Ventilation (L x min-1) was significantly (P < 0.05) higher in ML compared with EF during all three conditions (mean +/- SE) (rest: 12.4 +/- 0.7 vs 10.3 +/- 0.8; 55% VO2max: 46.2 +/- 0.9 vs 42.2 +/- 1.4; and 80% VO2max: 68.8 +/- 3.0 vs 63.3 +/- 2.0 L x min-1, respectively). Resting VO2 (mL x kg-1 x min-1) was significantly (P < 0.05) hi gher in ML (4.8 +/- 0.1) compared with EF (3.9 +/- 0.2). Profile of Mood States (POMS) total mood disturbance (TMD) and three subscale (depression, fatigue, and confusion) scores were also significantly higher during ML compared with EF; TMD: 127 +/- 6.0 vs 104 +/- 6.0; depression: 6 +/- 1.4 vs 3 +/- 1.4; fatigue: 9 +/- 1.0 vs 4 +/- 0.9; and confusion: 7 +/- 0.9 vs 5 +/- 1.2, respectively. The POMS vigor subscale score was significantly lower during ML (11 +/- 1.5) when compared with EF (19 +/- 0.7). RE at speeds corresponding to 55% VO2max was not significantly different between phases of the menstrual cycle. RE at speeds corresponding to 80% VO2max was, however, significantly less (higher VO2) during ML (41.4 +/- 0.8 mL x kg-1 x min-1) than EF (40.2 +/- 0.5 mL x kg-1 x min-1). It was concluded that RE at speeds corresponding to 80% VO2max in moderately-trained female runners covaries independently with ventilatory drive changes and with fluctuations in mood state which occur throughout the menstrual cycle.