What is the clinical evidence from this study?

Study design: Observational. Population: Healthy humans. Intervention: Cycling exercise (mild, moderate, and heavy) vs. Rest. Primary outcome: Dynamic cerebral autoregulation and steady-state changes in middle cerebral artery (MCA) velocity in relation to arterial pressure (p=<0.05).

December 10, 2004

Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans

Q: What are the key findings of this study?

Cycling exercise increased pulse pressure by up to 57% (P<0.05), but dynamic cerebral autoregulation remained able to modulate blood flow around the exercise-induced increase in mean MCA velocity.

Key Result

Cycling exercise increased pulse pressure by up to 57% (P<0.05), but dynamic cerebral autoregulation remained able to modulate blood flow around the exercise-induced increase in mean MCA velocity.

Study Design

Type

Observational

Structured PICO

How does dynamic exercise affect middle cerebral artery flow velocity and cerebral autoregulation in humans?

Population

Humans

Intervention

Mild, moderate, and heavy cycling exercise

Comparator

Rest

Outcome

Relationship between systolic, diastolic, and mean arterial pressure and middle cerebral artery blood flow velocity evaluated using transfer function analysissurrogate

Dynamic cerebral autoregulation remains able to modulate blood flow around the exercise-induced increase in mean middle cerebral artery velocity, even during high-intensity exercise.

Main Result

p-value: p=<0.05

Abstract

Exercise challenges cerebral autoregulation (CA) by a large increase in pulse pressure (PP) that may make systolic pressure exceed what is normally considered the upper range of CA. This study examined the relationship between systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) and systolic (V(s)), diastolic (V(d)). and mean (V(m)) middle cerebral artery (MCA) blood flow velocity during mild, moderate, and heavy cycling exercise. Dynamic CA and steady-state changes in MCA V in relation to changes in arterial pressure were evaluated using transfer function analysis. PP increased by 37% and 57% during moderate and heavy exercise, respectively (P < 0.05), and the pulsatility of MCA V increased markedly. Thus exercise increased MCA V(m) and V(s) (P < 0.05) but tended to decrease MCA V(d) (P = 0.06). However, the normalized low-frequency transfer function gain between MAP and MCA V(m) and between SBP and MCA V(s) remained unchanged from rest to exercise, whereas that between DBP and MCA V(d) increased from rest to heavy exercise (P < 0.05). These findings suggest that during exercise, CA is challenged by a rapid decrease rather than by a rapid increase in blood pressure. However, dynamic CA remains able to modulate blood flow around the exercise-induced increase in MCA V(m), even during high-intensity exercise.

Bookmark