title: Characterizing blood oxygen level-dependent (BOLD) response following in-magnet quadriceps exercise.
abstract: OBJECTIVE
  There have been no studies to investigate the effects of cycling exercise protocols, as well as repeated bouts of exercise, on the blood oxygen level-dependent (BOLD) response in the quadriceps muscles. This study characterized BOLD signal recovery following non-ischemic bouts of exercise in the quadriceps muscles of healthy adults in order to provide a basis for application of a protocol for clinical populations.
  
  
  METHODS
  Healthy male subjects (23.7 ± 2.0 years of age, n = 10) completed three cycles of one-minute exercise (65 % of maximum workload), with two minutes of rest between each bout, on an MRI-compatible ergometer. The BOLD responses during recovery were fitted to a sigmoid model, and response kinetics (post-exercise intensity [S0]), response time (α), change in baseline BOLD signal (κ), and inflection point (β)] were measured.
  
  
  RESULTS
  The sigmoid function fit well to the post-exercise BOLD data (r (2) = 0.95 ± 0.04). The mean response time was 10.5 ± 3.8 seconds, change in baseline BOLD intensity was 0.15 ± 0.068, and time to half-peak was 20.2 ± 8.6 seconds.
  
  
  CONCLUSIONS
  The proposed sigmoid model is a robust method for quantifying quadriceps BOLD response post-exercise without induced ischemia. Extension of this model to evaluate microvascular responses in patients with chronic disease could improve our understanding of exercise intolerance.
authors.affiliation: Department of Exercise Sciences, University of Toronto, Toronto, Canada.
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Caterini
authors.forename: Alyaa H
authors.initials: AH
authors.lastname: Elzibak
authors.forename: Emilie Jean
authors.initials: EJ
authors.lastname: St Michel
authors.forename: Brian W
authors.initials: BW
authors.lastname: McCrindle
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Redington
authors.forename: Sara
authors.initials: S
authors.lastname: Thompson
authors.forename: Michael D
authors.initials: MD
authors.lastname: Noseworthy
authors.forename: Greg D
authors.initials: GD
authors.lastname: Wells
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013848:Thigh
chemical_list: D010100:Oxygen