Aortic Reservoir Function is Attenuated Following Acute Endurance and Interval Exercise

Abstract

Aortic reservoir function is a measure of the aorta to function as a second pump during diastole and attenuate the effects of pulsatile blood flow. The effect of acute high vs. moderate exercise intensity on reservoir function is unknown. PURPOSE: To determine the effect of acute steady state (SS) and high-intensity interval (INT) exercise on reservoir function in well trained cyclists. METHODS: 20 competitive cyclists, M (n=14) and F (n=6), completed a high-intensity interval protocol consisting of 4 × 30 s high-intensity exercise bouts (Wingate tests) with 4.5 min active recovery between each bout. On a separate day, subjects completed an hour-long steady state cycling bout at 65% VO2 peak. VO2 peak was measured previously. The order of SS and INT exercise was randomized. Measurements were made at rest and 30 min post exercise. Aortic reservoir function was calculated as Diastolic Run-off (DR)/Stroke Volume (SV). DR was equal to Systemic Arterial Compliance (SAC) x End-Systolic Pressure (ESP)-Diastolic Pressure (DP). SAC was determined from Tau/TPR, and Tau was equal to diastolic time (DT)/ ln ESP-ln DP. All values were found 30 min post exercise. Statistical analysis was performed using ANOVAs with repeated measures (p<0.05). RESULTS: Average reservoir function at rest was 71%, which was significantly reduced to 51% (p<0.05) following SS exercise, but with a significantly greater reduction (from 67% to 33%, p<0.05) following INT exercise. DR was reduced significantly from 72 ml at rest to 48 ml following SS exercise (p<0.05) but the reduction in DR was significantly greater (p<0.05) post INT (from 65 ml to 28 ml). There were no significant changes in SAC following either SS or INT exercise. DT decreased significantly in both conditions but was significantly lower following INT exercise (858 ms to 680 ms 30 minutes post SS and 810 ms to 398 ms post INT; p<0.05). CONCLUSION: Aortic reservoir function is attenuated following acute SS and INT exercise, but these reductions were greater post INT suggesting that exercise intensity affects aortic reservoir function. These changes do not appear to be mediated by changes in SAC. The reduction in DT likely produced the lower aortic reservoir function, suggesting that reservoir function following exercise is primarily affected by heart rate and not by changes in arterial function per se.