Spatial heterogeneity of quadriceps muscle deoxygenation kinetics during cycle exercise.
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.
Koga
Shunsaku
S
Applied Physiology Laboratory, Kobe Design University, Kobe, Japan. s-koga@kobe-du.ac.jp
Poole
David C
DC
Ferreira
Leonard F
LF
Whipp
Brian J
BJ
Kondo
Narihiko
N
Saitoh
Tadashi
T
Ohmae
Etsuko
E
Barstow
Thomas J
TJ
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
D006454:Hemoglobins; D009211:Myoglobin; C100003:deoxyhemoglobin; D010100:Oxygen