Acute cardiovascular responses to the 100-mi Western States Endurance Run.

Ultramarathon participation is growing in popularity and exposes runners to unique stressors including extreme temperatures, high altitude, and exceedingly long exercise duration. However, the acute effects of ultramarathon participation on the cardiovascular system are not well understood. To determine the acute effects of trail ultramarathon participation on central artery stiffness and hemodynamics, 41 participants (9 F, 32 M) participating in the 2023 Western States Endurance Run underwent measures of carotid-femoral pulse wave velocity (cf-PWV) and pulse wave analysis pre- and <1 h post-race. Subendocardial viability ratio (SEVR) was calculated from central blood pressure (BP) waveforms. Serum was analyzed for creatine kinase (CK) activity as a measure of muscle damage. Normally distributed data are presented as means ± standard deviation (SD), and nonnormally distributed data are presented as median (interquartile range). Runners were middle-aged and generally lean [age = 44 ± 9 yr, body mass index (BMI) = 22.7 ± 1.8 kg·m^-2]. There was no difference in cf-PWV from pre- to post-race (pre = 6.4 ± 1.0, post = 6.2 ± 0.85 m/s, P = 0.104), a finding that persisted after adjusting for mean arterial pressure (P = 0.563). Systolic and diastolic BPs were lower post-race (pre = 129/77 ± 9/7, post = 122/74 ± 10/8 mmHg, P < 0.001). Augmentation index (AIx; pre = 17.3 ± 12.2, post = 6.0 ± 13.7%, P < 0.001), AIx normalized to a heart rate of 75 beats/min (P = 0.043), reflection magnitude (pre = 55.5(49.0-60.8), post = 45.5(41.8-48.8)%, P < 0.001), and SEVR (pre = 173.0(158.0-190.0), post = 127.5(116.5-145.8)%, P < 0.001) were reduced post-race. CK increased markedly from pre- to post-race (pre = 111(85-162), post = 11,973(5,049-17,954) U/L, P < 0.001). Completing a 161-km trail ultramarathon does not affect central arterial stiffness and acutely reduces BP despite eliciting profound muscle damage. However, the reduced post-race SEVR suggests a short-term mismatch between myocardial work and coronary artery perfusion.NEW AND NOTEWORTHY Ultramarathon participation is growing dramatically. However, the acute cardiovascular effects of completing a 161-km trail ultramarathon remain unknown. We examined the acute effects of completing the 2023 Western States Endurance Run on arterial stiffness and central hemodynamics in a relatively large sample of males and females. We observed dramatic postexercise hypotension, reductions in reflected wave amplitude and reduced subendocardial viability ratio post-race. These findings suggest that ultramarathon participation has few negative effects on cardiovascular health.