n South African Journal of Sports Medicine - Influence of menstrual phase on ventilatory responses to submaximal exercise : original research article




&lt;i&gt;Objectives.&lt;/i&gt; To determine whether an increase in respiratory drive, due to elevated progesterone and oestrogen concentration during various menstrual phases, persists throughout prolonged submaximal exercise and potentially contributes to fatigue. Furthermore, to determine whether the difference in the ventilatory response to exercise from one menstrual phase to another is correlated to the ovarian hormone concentrations. &lt;br&gt;&lt;i&gt;Design.&lt;/i&gt; We compared the change in ventilatory parameters during 90 min exercise at 60%VO&lt;sub&gt;2max&lt;/sub&gt; between the early follicular (EF) and mid-luteal (ML) phase (N = 9) and between the EF and late follicular (LF) phase (N = 5) in eumenorrhoeic women. <br><i>Main outcome measures.&lt;/i&gt; Menstrual phase comparisons and correlations between the change in ventilatory parameters (minute ventilation (V<sub>E</sub>), respiratory rate (RR), tidal volume) from the EF to ML or from the EF to LF phase and ovarian hormone concentration. &lt;br&gt;&lt;i&gt;Results.&lt;/i&gt; The difference in RR between EF and ML phases correlated to progesterone concentration in the ML phase (r = 0.7, p = 0.04). In addition, RR was higher during exercise in the ML compared with EF phase for the full duration of exercise by on average 2.3 ± 2.1 breaths/min (p < 0.05). However, no difference in submaximal VO&lt;sub&gt;2&lt;/sub&gt; between menstrual phases was evident. No significant difference in exercising-V&lt;sub&gt;E&lt;/sub&gt; was observed between menstrual phases, but the change in V&lt;sub&gt;E&lt;/sub&gt; from EF to ML correlated to oestrogen (r = 0.8, p = 0.02) and progesterone (r = 0.7, p = 0.04) concentration in the ML phase. &lt;br&gt;&lt;i&gt;Conclusions.&lt;/i&gt; The change in ventilatory parameters from EF to ML phase is related to the ovarian hormone concentrations. Therefore inter-individual variability should be considered in menstrual phase comparative studies. Furthermore, the persistently higher RR noted during exercise in the ML phase did not increase metabolic rate, and is therefore not expected to affect rate of fatigue significantly, even during prolonged exercise.


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