Arterial Stiffness and Subendocardial Viability Ratio: Temporal Responses to Ultra-Endurance Exercise.

Ultra-endurance exercise causes significant cardiovascular stress, yet the vascular responses during recovery remain incompletely understood. This study examined the short- (12-18 hours) and longer-term (7 and 28 days) effects of a long-distance triathlon on arterial stiffness and subendocardial viability ratio (SEVR) in novice triathletes. Eleven participants (2 females, 9 males), novice to long-distance exercise events, completed cardiovascular assessments at baseline (pre-race), 12-18 hours post-race, and 7- and 28-days post-race. Measures included carotid-femoral pulse wave velocity (PWV), augmentation index (Aix) and SEVR, obtained via applanation tonometry. PWV remained unchanged at all post-exercise time points (P = 0.310). Aix showed significant reduction at 7 days post-event (P = 0.024), though this effect was abolished after normalizing values to a heart rate of 75 beats per minute (Aix75, P = 0.162). SEVR decreased significantly 12-18 hours post-race (P < 0.001), indicating a transient imbalance between myocardial supply and demand, likely driven by elevated heart rates and reduced diastolic perfusion time. SEVR returned to baseline by 7 days post-event. These findings suggest that while no sustained changes in arterial stiffness were observed, hemodynamic conditions during recovery may signify altered myocardial supply-demand balance in novice athletes. Further research is needed to explore these mechanisms, with enhanced temporal resolution, to better understand the cardiovascular implications for novice endurance athletes.