title: Limitations of respiratory muscle and vastus lateralis blood flow during continuous exercise.
abstract: Measurement of regional blood flow to the respiratory muscles has traditionally been invasive. The blood flow index (BFI), a minimally invasive method using indocyanine green dye (ICG) and near infrared spectroscopy, allows assessment of within subject changes in regional blood flow. This study assessed regional BFI to the vastus lateralis muscle (QBFI) and the superficial respiratory muscles in the seventh intercostal space (RMBFI). Eight healthy subjects cycled continuously at incrementally more difficulty stages to exhaustion. In our subjects, QBFI declined between 83% and 100% of maximal exertion (p=0.002) and no statistically significant changes in RMBFI were seen despite steadily increasing ventilatory workloads. Post hoc pairwise comparisons demonstrated that QBFI at 83% work (0.015μmoless(-1)±0.005) was significantly higher than at maximum work output (0.011μmoless(-1)±0.004, p=0.007). There were no other significant differences of QBFI between maximum work output and different levels of work. The current study suggests that respiratory and locomotor muscle blood flow during sub-maximal and maximal exertion is unable to match increasing workloads.
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada. william.henderson@vch.ca
authors.forename: William R
authors.initials: WR
authors.lastname: Henderson
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Guenette
authors.forename: Paolo B
authors.initials: PB
authors.lastname: Dominelli
authors.forename: Donald E G
authors.initials: DE
authors.lastname: Griesdale
authors.forename: Jordan S
authors.initials: JS
authors.lastname: Querido
authors.forename: Robert
authors.initials: R
authors.lastname: Boushel
authors.forename: A William
authors.initials: AW
authors.lastname: Sheel
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D004396:Coloring Agents; D003935:Diagnostic Techniques, Cardiovascular; D005080:Exercise Test; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007208:Indocyanine Green; D008297:Male; D018670:Monitoring, Ambulatory / Q000379:methods; D018763:Muscle Fatigue / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D052097:Quadriceps Muscle / Q000098:blood supply* / Q000502:physiology; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology; D012132:Respiratory Muscles / Q000098:blood supply* / Q000502:physiology; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D014939:Work of Breathing / Q000502:physiology; D055815:Young Adult
chemical_list: D004396:Coloring Agents; D007208:Indocyanine Green