title: Reduced heterogeneity of muscle deoxygenation during heavy bicycle exercise.
abstract: OBJECTIVE
  This study evaluated heterogeneity of muscle O2 dynamics in a single muscle during bicycle exercise using an eight-channel near-infrared continuous wave spectroscopy (NIRcws) mapping system.
  
  
  METHODS
  Nine healthy subjects performed bicycle exercise at fixed workloads of 20, 40, 60, 80, and 100% maximal workload for 5 min at each level. Muscle oxygenation in the vastus lateralis (VL) during and after each exercise was monitored using the NIRcws mapping system. Pulmonary O2 uptake and heart rate were monitored continuously during the experiment. Blood samples were taken to measure blood lactate concentration at 30 s after each exercise stage.
  
  
  RESULTS
  Half time reoxygenation, the time taken to reach a value of half-maximal recovery, was significantly delayed in distal sites compared with proximal sites of VL. Conversely, muscle deoxygenation for all measurement sites increased incrementally with higher exercise workloads, and no significant difference of deoxygenation level showed within each channel. However, relative dispersion of muscle deoxygenation during exercise significantly decreased when the workload increased. Moreover, relative dispersion of muscle deoxygenation between the subjects also decreased with an increase in the workload.
  
  
  CONCLUSIONS
  Muscle deoxygenation in a single muscle was more heterogeneous at lower exercise workloads, and variations of the muscle deoxygenation heterogeneity between subjects were greater at lower exercise workloads.
authors.affiliation: Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA. kime@tokyo-med.ac.jp
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Kime
authors.forename: Joohee
authors.initials: J
authors.lastname: Im
authors.forename: Daniel
authors.initials: D
authors.lastname: Moser
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Lin
authors.forename: Shoko
authors.initials: S
authors.lastname: Nioka
authors.forename: Toshihito
authors.initials: T
authors.lastname: Katsumura
authors.forename: Britton
authors.initials: B
authors.lastname: Chance
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D013647:Task Performance and Analysis
chemical_list: D010100:Oxygen