title: Spatial heterogeneity of quadriceps muscle deoxygenation kinetics during cycle exercise.
abstract: To test the hypothesis that, during exercise, substantial heterogeneity of muscle hemoglobin and myoglobin deoxygenation [deoxy(Hb + Mb)] dynamics exists and to determine whether such heterogeneity is associated with the speed of pulmonary O(2) uptake (pVo(2)) kinetics, we adapted multi-optical fibers near-infrared spectroscopy (NIRS) to characterize the spatial distribution of muscle deoxygenation kinetics at exercise onset. Seven subjects performed cycle exercise transitions from unloaded to moderate [<gas exchange threshold (GET)] and heavy (>GET) work rates and the relative changes in deoxy(Hb + Mb), at 10 sites in the quadriceps, were sampled by NIRS. At exercise onset, the time delays in muscle deoxy(Hb + Mb) were spatially inhomogeneous [intersite coefficient of variation (CV), 3~56% for <GET, 2~21% for >GET]. The primary component kinetics (time constant) of muscle deoxy(Hb + Mb) reflecting increased O(2) extraction were also spatially inhomogeneous (intersite CV, 6~48% for <GET, 7~47% for >GET) and faster (P < 0.05) than those of phase 2 pVo(2). However, the degree of dynamic intersite heterogeneity in muscle deoxygenation did not correlate significantly with phase 2 pVo(2) kinetics. In conclusion, the dynamics of quadriceps microvascular oxygenation demonstrates substantial spatial heterogeneity that must arise from disparities in the relative kinetics of Vo(2) and O(2) delivery increase across the regions sampled.
authors: Applied Physiology Laboratory, Kobe Design University, Kobe, Japan. s-koga@kobe-du.ac.jp
authors: Shunsaku
authors: S
authors: Koga
authors: David C
authors: DC
authors: Poole
authors: Leonard F
authors: LF
authors: Ferreira
authors: Brian J
authors: BJ
authors: Whipp
authors: Narihiko
authors: N
authors: Kondo
authors: Tadashi
authors: T
authors: Saitoh
authors: Etsuko
authors: E
authors: Ohmae
authors: Thomas J
authors: TJ
authors: Barstow
mesh_terms: D000328:Adult; D001642:Bicycling; D015444:Exercise / Q000502:physiology*; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008297:Male; D008833:Microcirculation / Q000378:metabolism; D009119:Muscle Contraction; D009211:Myoglobin / Q000378:metabolism; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D052097:Quadriceps Muscle / Q000098:blood supply / Q000378:metabolism*; D012107:Research Design; D019265:Spectroscopy, Near-Infrared
chemical_list: D006454:Hemoglobins; D009211:Myoglobin; C100003:deoxyhemoglobin; D010100:Oxygen