PMID- 37439241
OWN - NLM
STAT- MEDLINE
DCOM- 20230821
LR  - 20230823
IS  - 1522-1601 (Electronic)
IS  - 0161-7567 (Linking)
VI  - 135
IP  - 3
DP  - 2023 Sep 1
TI  - The effect of increasing work rate amplitudes from a common metabolic baseline on 
      the kinetic response of V̇o(2p), blood flow, and muscle deoxygenation.
PG  - 584-600
LID - 10.1152/japplphysiol.00566.2022 [doi]
AB  - A step-transition in external work rate (WR) increases pulmonary O(2) uptake 
      (V̇o(2p)) in a monoexponential fashion. Although the rate of this increase, 
      quantified by the time constant (tau), has frequently been shown to be similar 
      between multiple different WR amplitudes (DeltaWR), the adjustment of O(2) delivery 
      to the muscle (via blood flow; BF), a potential regulator of V̇o(2p) kinetics, 
      has not been extensively studied. To investigate the role of BF on V̇o(2p) 
      kinetics, 10 participants performed step-transitions on a knee-extension 
      ergometer from a common baseline WR (3 W) to: 24, 33, 45, 54, and 66 W. Each 
      transition lasted 8 min and was repeated four to six times. Volume turbinometry 
      and mass spectrometry, Doppler ultrasound, and near-infrared spectroscopy were 
      used to measure V̇o(2p), BF, and muscle deoxygenation (deoxy[Hb + Mb]), 
      respectively. Similar transitions were ensemble-averaged, and phase II V̇o(2p), 
      BF, and deoxy[Hb + Mb] were fit with a monoexponential nonlinear least squares 
      regression equation. With increasing DeltaWR, tauV̇o(2p) became larger at the higher 
      DeltaWRs (P < 0.05), while tauBF did not change significantly, and the mean response 
      time (MRT) of deoxy[Hb + Mb] became smaller. These findings that V̇o(2p) kinetics 
      become slower with increasing DeltaWR, while BF kinetics are not influenced by DeltaWR, 
      suggest that O(2) delivery could not limit V̇o(2p) in this situation. However, 
      the speeding of deoxy[Hb + Mb] kinetics with increasing DeltaWR does imply that the 
      O(2) delivery-to-O(2) utilization of the microvasculature decreases at higher 
      DeltaWRs. This suggests that the contribution of O(2) delivery and O(2) extraction to 
      V̇O(2) in the muscle changes with increasing DeltaWR.NEW & NOTEWORTHY A step increase 
      in work rate produces a monoexponential increase in V̇o(2p) and blood flow to a 
      new steady-state. We found that step transitions from a common metabolic baseline 
      to increasing work rate amplitudes produced a slowing of V̇o(2p) kinetics, no 
      change in blood flow kinetics, and a speeding of muscle deoxygenation kinetics. 
      As work rate amplitude increased, the ratio of blood flow to V̇o(2p) became 
      smaller, while the amplitude of muscle deoxygenation became greater. The gain in 
      vascular conductance became smaller, while kinetics tended to become slower at 
      higher work rate amplitudes.
FAU - Love, Lorenzo K
AU  - Love LK
AUID- ORCID: 0000-0002-7543-2639
AD  - Canadian Centre for Activity and Aging, The University of Western Ontario, 
      London, Ontario, Canada.
AD  - School of Kinesiology, Faculty of Health Sciences, The University of Western 
      Ontario, London, Ontario, Canada.
AD  - Department of Kinesiology and Physical Education, Redeemer University, Ancaster, 
      Ontario, Canada.
FAU - Hodgson, Michael D
AU  - Hodgson MD
AD  - Canadian Centre for Activity and Aging, The University of Western Ontario, 
      London, Ontario, Canada.
AD  - School of Kinesiology, Faculty of Health Sciences, The University of Western 
      Ontario, London, Ontario, Canada.
FAU - Keir, Daniel A
AU  - Keir DA
AUID- ORCID: 0000-0002-5656-373X
AD  - Canadian Centre for Activity and Aging, The University of Western Ontario, 
      London, Ontario, Canada.
AD  - School of Kinesiology, Faculty of Health Sciences, The University of Western 
      Ontario, London, Ontario, Canada.
AD  - Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario, 
      Canada.
FAU - Kowalchuk, John M
AU  - Kowalchuk JM
AUID- ORCID: 0009-0009-6799-3960
AD  - Canadian Centre for Activity and Aging, The University of Western Ontario, 
      London, Ontario, Canada.
AD  - School of Kinesiology, Faculty of Health Sciences, The University of Western 
      Ontario, London, Ontario, Canada.
AD  - Department of Kinesiology and Physical Education, Redeemer University, Ancaster, 
      Ontario, Canada.
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20230713
PL  - United States
TA  - J Appl Physiol (1985)
JT  - Journal of applied physiology (Bethesda, Md. : 1985)
JID - 8502536
RN  - S88TT14065 (Oxygen)
SB  - IM
MH  - Humans
MH  - *Oxygen Consumption/physiology
MH  - *Exercise/physiology
MH  - Lung/physiology
MH  - Pulmonary Gas Exchange/physiology
MH  - Muscle, Skeletal/physiology
MH  - Kinetics
MH  - Oxygen/metabolism
OTO - NOTNLM
OT  - V̇o2p kinetics
OT  - blood flow kinetics
OT  - exercise intensity domains
OT  - muscle deoxygenation
OT  - vascular conductance
EDAT- 2023/07/13 06:42
MHDA- 2023/08/21 06:42
CRDT- 2023/07/13 05:34
PHST- 2023/08/21 06:42 [medline]
PHST- 2023/07/13 06:42 [pubmed]
PHST- 2023/07/13 05:34 [entrez]
AID - 10.1152/japplphysiol.00566.2022 [doi]
PST - ppublish
SO  - J Appl Physiol (1985). 2023 Sep 1;135(3):584-600. doi: 
      10.1152/japplphysiol.00566.2022. Epub 2023 Jul 13.