Spatial heterogeneity of quadriceps muscle deoxygenation kinetics during cycle exercise

• Published in: Journal of applied physiology (1985) 2007-12, Vol.103 (6), p.2049-2056
• Main Authors: Koga, Shunsaku, Poole, David C, Ferreira, Leonard F, Whipp, Brian J, Kondo, Narihiko, Saitoh, Tadashi, Ohmae, Etsuko, Barstow, Thomas J
• Format: Article
• Language: English
• Subjects: Adult; Bicycling; Biological and medical sciences; Exercise; Exercise - physiology; Female; Fundamental and applied biological sciences. Psychology; Hemoglobin; Hemoglobins - metabolism; Humans; Hypothesis testing; Kinetics; Male; Microcirculation - metabolism; Muscle Contraction; Musculoskeletal system; Myoglobin - metabolism; Oxygen; Oxygen - blood; Oxygen Consumption; Pulmonary Gas Exchange; Quadriceps Muscle - blood supply; Quadriceps Muscle - metabolism; Research Design; Spectroscopy, Near-Infrared
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00627.2007

1 Applied Physiology Laboratory, Kobe Design University, Kobe, Japan; 3 University of Leeds, Leeds, United Kingdom; 4 Kobe University, Kobe, Japan; 5 Hamamatsu Photonics K. K., Hamakita, Japan; and 2 Department of Kinesiology, Anatomy, and Physiology, Kansas State University, Manhattan, Kansas Submitted 12 June 2007 ; accepted in final form 19 September 2007 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 (p O 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 [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]. 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) and faster (P < 0.05) than those of phase 2 p O 2 . However, the degree of dynamic intersite heterogeneity in muscle deoxygenation did not correlate significantly with phase 2 p O 2 kinetics. In conclusion, the dynamics of quadriceps microvascular oxygenation demonstrates substantial spatial heterogeneity that must arise from disparities in the relative kinetics of O 2 and O 2 delivery increase across the regions sampled. near-infrared spectroscopy; oxygen uptake kinetics; muscle oxygen delivery; muscle oxygen utilization Address for reprint requests and other correspondence: S. Koga, Applied Physiology Laboratory, Kobe Design Univ., 8-1-1 Gakuennishi-machi, Nishi-ku, Kobe, 651-2196, Japan (e-mail: s-koga{at}kobe-du.ac.jp )