Systemic and regional (including superior mesenteric) haemodynamic responses during supine exercise while fasted and fed in normal man

The systemic and regional (including superior mesenteric artery, SMA) responses to exercise in the fasting and fed state were studied in ten normal subjects before, during and after 9 min of graded supine bicycle exercise on two separate occasions, when fasted and after a liquid meal. During exercise, blood pressure (BP) and cardiac index rose similarly in both states. Resting SMA blood flow was higher when fed (519 (282-619) versus 240 (133-255) ml/min, p < 0.01). SMA blood flow fell during exercise in both states, to 98 (63-154) ml/min, p < 0.01 when fasted and to 55 (42-149) ml/min, p < 0.01 when fed. SMA vascular resistance rose during exercise in bath states, but rose less when fasted by 36 (6-57)% versus 143 (36-240)% (NS). Resting forearm and leg blood now (FBF and LBF) and vascular resistance (FVR and LVR) were similar fasted and fed. FBF and FVR did not change after exercise in either state. LBF rose and LVR fell similarly in both states. We conclude that in normal subjects, although splanchnic oxygen demand is likely to be greater after food, during light to moderate exercise splanchnic vasoconstriction contributes to maintenance of BP.