The Effects of Menstrual Cycle Phase on Gastrointestinal Responses to a Simulated Football Match

This study evaluated the effects of a simulated football match on gastrointestinal (GI) symptoms, damage and indirect markers of gut barrier integrity, and investigated whether GI responses are modulated by menstrual cycle (MC) phase. Twelve eumenorrheic females completed two 45-min bouts of an intermittent treadmill protocol, replicating the activity profile of a football match, during Phase 1 (P1, days 1-5) and Phase 4 (P4, 6-8 days following a positive ovulation test) of their MC. Global GI discomfort was recorded every 15 min during exercise, and specific GI symptoms were assessed at rest, half-time (HT), full-time (FT) and 60 min post-exercise (POST-60). Blood samples were collected at rest, FT and POST-60 to assess intestinal fatty-acid binding protein (I-FABP), lipopolysaccharide binding protein (LBP), soluble cluster of differentiation 14 (sCD14) and claudin-3 (CLDN-3). I-FABP increased by 51% from rest to FT (p = 0.007), but there was no effect of exercise on LBP, CLDN-3 or sCD14. Global GI discomfort was 65% greater in P1, than P4 (p = 0.006) and total GI symptom score was greater in P1 than P4 at rest (p = 0.011) and FT (p = 0.021). CLDN-3 concentrations were greater in P1 than P4 at rest (p = 0.02) and POST-60 (p = 0.03). There were no differences between MC phase for I-FABP, LBP or sCD14. Participants experienced increased GI discomfort during P1 compared to P4 of the MC, at rest and during exercise. However, exercise-induced GI symptoms and damage occurred at a similar rate in both MC phases.