Sex-Specific Physiological Responses to Ultramarathon

Purpose Despite a growing body of literature on the physiological responses to ultramarathon, there is a paucity of data in females. This study assessed the female physiological response to ultramarathon and compared the frequency of perturbations to a group of race- and time-matched males. Methods Data were collected from 53 contestants of an ultramarathon trail race at the Ultra-Trail du Mont-Blanc (UTMB (R)) in 2018/19. Before and within 2 h of the finish, participants underwent physiological assessments, including blood sampling for biomarkers (creatine kinase-MB isoenzyme [CK-MB], cardiac troponin I [cTnI], brain natriuretic peptide [BNP], and creatinine [Cr]), pulmonary function testing (spirometry, exhaled NO, diffusing capacities, and mouth pressures), and transthoracic ultrasound (lung comet tails, cardiac function). Data from eight female finishers (age = 36.6 +/- 6.9 yr; finish time = 30:57 +/- 11:36 h:min) were compared with a group of eight time-matched males (age = 40.3 +/- 8.3 yr; finish time = 30:46 +/- 10:32 h:min). Results Females exhibited significant pre- to postrace increases in BNP (25.8 +/- 14.6 vs 140.9 +/- 102.7 pg.mL(-1); P = 0.007) and CK-MB (3.3 +/- 2.4 vs 74.6 +/- 49.6 IU.L-1; P = 0.005), whereas males exhibited significant pre- to postrace increases in BNP (26.6 +/- 17.5 vs 96.4 +/- 51.9 pg.mL(-1); P = 0.002), CK-MB (7.2 +/- 3.9 vs 108.8 +/- 37.4 IU.L-1; P = 0.002), and Cr (1.06 +/- 0.19 vs 1.23 +/- 0.24 mg.dL(-1); P = 0.028). Lung function declined in both groups, but males exhibited additional reductions in lung diffusing capacities (DLCO = 34.4 +/- 5.7 vs 29.2 +/- 6.9 mL.min(-1).mm Hg-1, P = 0.004; DLNO = 179.1 +/- 26.2 vs 152.8 +/- 33.4 mL.min(-1).mm Hg-1, P = 0.002) and pulmonary capillary blood volumes (77.4 +/- 16.7 vs 57.3 +/- 16.1 mL; P = 0.002). Males, but not females, exhibited evidence of mild postrace pulmonary edema. Pooled effect sizes for within-group pre- to postrace changes, for all variables, were generally larger in males versus females (d = 0.86 vs 0.63). Conclusions Ultramarathon negatively affects a range of physiological functions but generally evokes more frequent perturbations, with larger effect sizes, in males compared to females with similar race performances.