Quiet standing after carbohydrate ingestion induces sympathoexcitatory and pressor responses in young healthy males

- Standing after eating requires appropriate autonomic neural responses.
- Cardiovascular responses during standing after carbohydrate ingestion were examined.
- ECG and finger BP were recorded lying and standing after eating.
- After eating, SBP LF power increased with a rise in BP during standing.
- The data suggest central sympathetic activation mediated by baroreflex resetting.

ObjectiveTo investigate the role of the sympathetic nervous system in the cardiovascular response to quiet standing in the postprandial state.MethodFollowing a 30 min pre-ingestion phase, 14 healthy young male subjects consumed a 600 kcal carbohydrate-rich meal. Arterial blood pressure (BP) and heart rate (HR) were recorded for a further 120 min. Measurements were obtained (Finometer) in both the supine (5 min) and standing (5 min) condition every 30 min. Power spectral analysis of RR-interval and BP variability was calculated, and heart rate responses to the baroreceptor reflex were calculated to estimate spontaneous baroreflex sensitivity (sBRS). Derived stroke volume (SV) was measured to track changes to postural stress postprandially.ResultsQuiet standing increased RR-interval low frequency power, ratio of RR-interval low frequency power/high frequency power (ratio of RR LF/HF), and systolic BP low frequency power (SBP LF power), and decreased RR HF power and sBRS before, and after eating. After meal ingestion, SBP LF power increased and sBRS decreased in lying and standing conditions. During quiet standing postprandially, DBP and the mean arterial pressure increased (P < 0.01). The increased BP is associated with increased SV (P < 0.05) early postprandially, and increased SBP LF power (P < 0.01) in the later postprandial phase. SBP LF power is inversely correlated with SV postprandially (P < 0.001, R2 = 0.96).ConclusionThe findings suggest a sympathetic activation mediated by baroreflex resetting. Quiet standing in the postprandial state enhances sympathetic outflow to the vasculature, increasing BP. SV may be a compensatory factor stabilising BP during quiet standing early postprandially.