Muscle deoxygenation to VO2 relationship differs in young subjects with varying τVO2

• Published in: European journal of applied physiology Vol. 111; no. 12; pp. 3107 - 3118
• Main Authors: Murias, Juan M., Spencer, Matthew D., Kowalchuk, John M., Paterson, Donald H.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2011; Springer
• Subjects: Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Fundamental and applied biological sciences. Psychology; Human Physiology; Occupational Medicine/Industrial Medicine; Original Article; Sports Medicine; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Extraction; Blood flow distribution; Distribution; O; Near-infrared spectroscopy; Human; Deoxygenation; Hemodynamics; Striated muscle; Blood flow
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-011-1937-9

The relationship between the adjustment of muscle deoxygenation (∆[HHb]) and phase II V O 2p was examined in subjects presenting with a range of slow to fast V O 2p kinetics. Moderate intensity V O 2p and ∆[HHb] kinetics were examined in 37 young males (24 ± 4 years). V O 2p was measured breath-by-breath. Changes in ∆[HHb] of the vastus lateralis muscle were measured by near-infrared spectroscopy. V O 2p and ∆[HHb] response profiles were fit using a mono-exponential model, and scaled to a relative % of the response (0–100%). The ∆[HHb]/∆ V O 2p ratio for each individual (reflecting the matching of O 2 distribution to O 2 utilization) was calculated as the average ∆[HHb]/∆ V O 2p response from 20 to 120 s during the exercise on-transient. Subjects were grouped based on individual phase II V O 2p time-constant (τ V O 2p ): <21 s [very fast (VF)]; 21–30 s [fast (F)]; 31–40 s [moderate (M)]; >41 s [slow (S)]. The corresponding ∆[HHb]/∆ V O 2p were 0.98 (VF), 1.05 (F), 1.09 (M), and 1.22 (S). The larger ∆[HHb]/∆ V O 2p in the groups with slower V O 2p kinetics resulted in the ∆[HHb]/∆ V O 2p displaying a transient “overshoot” relative to the subsequent steady state level, which was progressively reduced as τ V O 2 became smaller ( r  = 0.91). When τ V O 2p  > ~20 s, the rate of adjustment of phase II V O 2p appears to be mainly constrained by the matching of local O 2 distribution to muscle V O 2 . These data suggest that in subjects with “slower” V O 2 kinetics, the rate of adjustment of V O 2 may be constrained by O 2 availability within the active tissues related to the matching of microvascular O 2 distribution to muscle O 2 utilization.