Effect of Cycling Exercise on Dynamic Cerebral Autoregulation in Humans

Abstract

We sought to explore the effect of cycling exercise of gradually increasing intensity on dynamic cerebral autoregulation (dCA) in humans. Ten healthy human subjects (seven men and three women; age, 27 ± 1 years, height, 176 ± 4 cm, weight, 76± 4 kg; mean ± SE) volunteered to participate in the present investigation. Their baseline data was collecting during 15 min of rest in a seated position on the cycle ergometer. Following rest, subjects pedaled at the rate of 60 rpm at mild workload (10W) for 10 min [Ex80, heart rate (HR) 88±4 bpm]. After 10 min of mild intensity exercise, the workload was increased to raise and mainatain steady-state HR at 130 bpm (Ex130). Subjects exercised at this moderate intensity for 10 min. A significant increase was found in plasma norepinephrine (NE) from rest to Ex130 (mean ± SEM, 1.8 ± 0.2 pml/ml to 3.2 ± 0.3 pml/ml, P<0.05). In addition, a significant decrease in low frequency (LF) (0.07–0.2 Hz) transfer function gain was observed at Ex130 in comparison to rest (0.88 ± 0.08 to 0.72 ± 0.05, P < 0.05) indicating an increase in dCA. The coherence between mean arterial pressure and middle cerebral artery velocity for all the exercise conditions remained greater than 0.5. These findings indicate that increased sympathetic nerve activity during cycling exercise is associated with increased dynamic cerebral autoregulation. The study was partially funded by Cardiovascular Research Institute and Tx-ACSM