Abstract and Introduction
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®) 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.
Ultramarathons are footraces that typically range from ~30 miles (~50 km) to ~150 miles (~240 km) in a single stage and considerably further in multistage events. Participation evokes extreme physiological strain on multiple body systems, particularly the cardiovascular and respiratory systems. For instance, studies show decreased left ventricular function and increased cardiac biomarkers after ultramarathon,[3,4] in addition to lung function derangements of 10%–15% with or without evidence of airway obstruction. Moreover, although most physiological perturbations are transient and generally recover to baseline within a week, there is the potential for long-term maladaptations and associated health issues. For these reasons, there is now a greater emphasis on understanding the acute and chronic physiological and pathophysiological responses to ultramarathon running.[1,2,6,7]
Despite the growing body of work, there is a paucity of data in female athletes. A recent review on pulmonary responses to marathon and ultramarathon running collated 15 studies with a cumulative 232 participants of which only 19 (8%) were females. This number is considerably below the estimated ~20% of female ultramarathon contestants[8–10] and supports the notion that females may be underrepresented in exercise science research. Potential explanations may be a researcher bias that favors males as recruitment participants, but also a possible volunteer bias that has males more willing to participate in exercise-related research. Nevertheless, anatomical and physiological differences between males and females can influence the exercise response,[14–17] and failure to consider these differences may limit the specificity of training programs and negatively affect efforts at promoting competitive longevity.
The issue of sex-based physiological predisposition to ultramarathon has also been a topic of recent discussion. Indeed, a number of exceptional, record-breaking performances by female athletes in ultramarathon in recent years has roused speculation that they might be predisposed to success in such events. The male-to-female performance gap in regular endurance sports like marathon is ~10%, but studies have calculated the performance gap in ultramarathon to be as low as 4%. In some instances, female performances may surpass those of their male counterparts. Additionally, in ultramarathon, there are distinct performance predictors for males (e.g., age, BMI, and years of running) and females (e.g., weekly running mileage and half-marathon record). Thus, although the question of whether females are physiologically predisposed to ultramarathon has not been directly explored, an ability to better tolerate the physiological stress of racing is likely ergogenic in ultramarathon and may also lead to better long-term health management.
Accordingly, there were two aims of this exploratory study. The first was to provide novel data on the physiological responses of females to an ultramarathon trail race, with specific emphasis on respiratory and cardiopulmonary function. The second was to explore sex differences in the frequency of pre- to postrace physiological perturbations in males and females matched for ultramarathon finish time.
Med Sci Sports Exerc. 2022;54(10):1647-1656. © 2022 American College of Sports Medicine