title: Middle cerebral artery diameter changes during rhythmic handgrip exercise in humans.
abstract: 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.
authors.affiliation: 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Verbree
authors.affiliation: 2 Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.|3 Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Agt
authors.initials: A
authors.lastname: Bronzwaer
authors.affiliation: 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: van Buchem
authors.affiliation: 4 Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Mjap
authors.initials: M
authors.lastname: Daemen
authors.affiliation: 2 Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.|3 Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Amsterdam, The Netherlands.|5 MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Nottingham, UK.
authors.forename: J J
authors.initials: JJ
authors.lastname: van Lieshout
authors.affiliation: 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Mjp
authors.initials: M
authors.lastname: van Osch
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D026241:Exercise Movement Techniques; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017585:Ultrasonography, Doppler, Transcranial; D014661:Vasoconstriction / Q000502:physiology*; D055815:Young Adult
keywords: Transcranial Doppler; cerebral blood flow; cerebral blood flow measurement; exercise; magnetic resonance angiography; magnetic resonance imaging