Middle cerebral artery diameter changes during rhythmic handgrip exercise in humans

• Published in: Journal of cerebral blood flow and metabolism Vol. 37; no. 8; pp. 2921 - 2927
• Main Authors: Verbree, J, Bronzwaer, AGT, van Buchem, MA, Daemen, MJAP, van Lieshout, JJ, van Osch, MJP
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.08.2017
• Subjects: Adult; Blood Flow Velocity - physiology; Cerebrovascular Circulation - physiology; Exercise - physiology; Exercise Movement Techniques; Female; Hand Strength - physiology; Heart Rate - physiology; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Middle Cerebral Artery - anatomy & histology; Middle Cerebral Artery - diagnostic imaging; Middle Cerebral Artery - physiopathology; Original; Ultrasonography, Doppler, Transcranial; Vasoconstriction - physiology; Young Adult; exercise; cerebral blood flow; magnetic resonance imaging; Transcranial Doppler; magnetic resonance angiography; cerebral blood flow measurement
• ISSN: 0271-678X; 1559-7016; 1559-7016
• DOI: 10.1177/0271678X16679419

Transcranial Doppler (TCD) sonography is a frequently employed technique for quantifying cerebral blood flow by assuming a constant arterial diameter. Given that exercise increases arterial pressure by sympathetic activation, we hypothesized that exercise might induce a change in the diameter of large cerebral arteries. Middle cerebral artery (MCA) cross-sectional area was assessed in response to handgrip exercise by direct magnetic resonance imaging (MRI) observations. Twenty healthy subjects (11 female) performed three 5 min bouts of rhythmic handgrip exercise at 60% maximum voluntary contraction, alternated with 5 min of rest. High-resolution 7 T MRI scans were acquired perpendicular to the MCA. Two blinded observers manually determined the MCA cross-sectional area. Sufficient image quality was obtained in 101 MCA-scans of 19 subjects (age-range 20–59 years). Mixed effects modelling showed that the MCA cross-sectional area decreased by 2.1 ± 0.8% (p = 0.01) during handgrip, while the heart rate increased by 11 ± 2% (p < 0.001) at constant end-tidal CO2 (p = 0.10). In conclusion, the present study showed a 2% decrease in MCA cross-sectional area during rhythmic handgrip exercise. This further strengthens the current concept of sympathetic control of large cerebral arteries, showing in vivo vasoconstriction during exercise-induced sympathetic activation. Moreover, care must be taken when interpreting TCD exercise studies as diameter constancy cannot be assumed.