title: Quantification of extra-cerebral and cerebral hemoglobin concentrations during physical exercise using time-domain near infrared spectroscopy.
abstract: Fitness is known to have beneficial effects on brain anatomy and function. However, the understanding of mechanisms underlying immediate and long-term neurophysiological changes due to exercise is currently incomplete due to the lack of tools to investigate brain function during physical activity. In this study, we used time-domain near infrared spectroscopy (TD-NIRS) to quantify and discriminate extra-cerebral and cerebral hemoglobin concentrations and oxygen saturation (SO2) in young adults at rest and during incremental intensity exercise. In extra-cerebral tissue, an increase in deoxy-hemoglobin (HbR) and a decrease inSO2were observed while only cerebralHbRincreased at high intensity exercise. Results in extra-cerebral tissue are consistent with thermoregulatory mechanisms to dissipate excess heat through skin blood flow, while cerebral changes are in agreement with cerebral blood flow (CBF) redistribution mechanisms to meet oxygen demand in activated regions during exercise. No significant difference was observed in oxy- (HbO2) and total hemoglobin (HbT). In additionHbO2,HbRandHbTincreased with subject's peak power output (equivalent to the maximum oxygen volume consumption;VO2peak) supporting previous observations of increased total mass of red blood cells in trained individuals. Our results also revealed known gender differences with higher hemoglobin in men. Our approach in quantifying both extra-cerebral and cerebral absolute hemoglobin during exercise may help to better interpret past and future continuous-wave NIRS studies that are prone to extra-cerebral contamination and allow a better understanding of acute cerebral changes due to physical exercise.
authors.affiliation: Institute of Biomedical Engineering, Université de Montréal, Montréal, QC, Canada; Centre Hospitalier Universitaire Sainte-Justine, Montréal, QC, Canada.
authors.forename: Héloïse
authors.initials: H
authors.lastname: Auger
authors.affiliation: Institut Universitaire de Gériatrie de Montréal, Montréal, QC, Canada; PERFORM Centre, Concordia University, Montréal, QC, Canada.
authors.forename: Louis
authors.initials: L
authors.lastname: Bherer
authors.affiliation: Centre Hospitalier Universitaire Sainte-Justine, Montréal, QC, Canada.
authors.forename: Étienne
authors.initials: É
authors.lastname: Boucher
authors.affiliation: Institut Universitaire de Gériatrie de Montréal, Montréal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Hoge
authors.affiliation: Institute of Biomedical Engineering, Université de Montréal, Montréal, QC, Canada; Department of Electrical Engineering, École Polytechnique de Montréal, Montréal, QC, Canada.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lesage
authors.affiliation: Institute of Biomedical Engineering, Université de Montréal, Montréal, QC, Canada; Centre Hospitalier Universitaire Sainte-Justine, Montréal, QC, Canada; Department of Radiology, Radio-Oncology and Nuclear Medicine, Université de Montréal, Montréal, QC, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Dehaes
keywords: (170.0110) Imaging systems; (170.1470) Blood or tissue constituent monitoring; (300.6500) Spectroscopy, time-resolved