UC San Diego

It is well documented that MAP decreases after aerobic exercise due to factors such as reduced TPR, maintained vasodilation in previously active muscles, reduced sympathetic innervation, and resetting of baroreceptors. Even with a significant decrease in MAP, it has been shown that cerebrovascular function, middle cerebral arterial flow velocity, and CPP are well-maintained. CPP, the pressure gradient that drives cerebral blood flow, is defined as the different between MAP and ICP. Thus, it was hypothesized that ICP will concomitantly decrease with MAP to maintain CPP and allow for adequate blood supply to the cerebrum.

To test this hypothesis, 17 healthy human subjects were recruited to complete a 30-minute period of stationary cycling. Measurements of ICP, MAP, TPR, and HR were taken before exercise to serve as a baseline; one hour of follow-up measurements were collected and compared to baseline values. It was discovered that ICP significantly decreased after stationary cycling (ANOVA P=0.0352) in conjunction with a significant decrease in MAP (ANOVA P=0.0025) and TPR (ANOVA P<0.0001). HR was elevated for the entire hour after exercise (ANOVA P<0.0001).

Sixteen of the subjects had their ICP estimated non-invasively while one of the subjects had their ICP measured invasively. The non-invasive ICP results closely matched the invasive ICP results and confirmed that the estimated ICP was accurate. These trends support my hypothesis that ICP decreases with MAP following moderate exercise.