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1 Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas, United States
2 Medical Pharmacology & Physiology; Dalton Cardiovascular Research Center, University of Missouri, Columbia, Columbia, Missouri, United States
3 Medical Pharmacology and Physiology; Dalton Cardiovascular Research Center, University of Missouri, Columbia, Columbia, United States
4 School of Sport and Exercise Science, University of Birmingham, Edgbaston, United Kingdom
5 Presbyterian Hospital of Dallas, Dallas, Texas, United States
6 Department of Anesthesia, University of Copenhagen, Copenhagen, Denmark
* To whom correspondence should be addressed. E-mail: sogoh{at}hsc.unt.edu.
We sought to examine the regulation of cerebral blood flow during 10 minutes of recovery from mild, moderate and heavy cycling exercise by measuring middle cerebral artery blood velocity (MCA V). Transfer function analyses between changes in arterial blood pressure and MCA V were used to assess the frequency components of dynamic cerebral autoregulation (CA). After mild and moderate exercise, the decreases in mean arterial pressure (MAP) and in mean MCA V (MCA Vm) were small. However, following heavy exercise MAP was rapidly and markedly reduced, whereas MCA Vm decreased slowly (-23±4 mmHg and -4±1 cm/s after one minute for MAP and MCA Vm, respectively; mean±SE). Importantly, for each workload, the normalized low frequency transfer function gain between MAP and MCA Vm remained unchanged from rest to exercise and during recovery indicating a maintained dynamic CA. Similar results were found for the systolic blood pressure and systolic MCA V relationship. In contrast, the normalized low frequency transfer function gain between diastolic blood pressure (DBP) and diastolic MCA V (MCA Vd) increased from rest to exercise and remained elevated in the recovery period (P<0.05). However, MCA Vd was quite stable upon the cessation of exercise. These findings suggest that MCA V is well maintained following mild to heavy dynamic exercise. However, the increased transfer function gain between DBP and MCA Vd suggests that dynamic CA becomes less effective in response to rapid decreases in blood pressure duirng the initial 10 minutes of recovery from dynamic exercise.
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