Impact of supine exercise on muscle deoxygenation kinetics heterogeneity: Mechanistic insights into slow pulmonary oxygen uptake dynamics

Goulding, Richie P and Okushima, Dai and Marwood, Simon and Poole, David and Barstow, Thomas and Tze-Huan, Lei and Narihiko, Kondo and Shunsaku, Koga (2020) Impact of supine exercise on muscle deoxygenation kinetics heterogeneity: Mechanistic insights into slow pulmonary oxygen uptake dynamics. Journal of Applied Physiology, 129 (3). pp. 535-546. ISSN 8750-7587

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Abstract

Oxygen uptake (V ̇O2) kinetics are slowed in the supine (S) position due to impaired muscle O2 delivery (Q ̇O2), however, these conclusions are predicated on single-site measurements in superficial muscle using continuous-wave near-infrared spectroscopy (NIRS). This study aimed to determine the impact of body position (i.e. upright [U] vs. S) on deep and superficial muscle deoxygenation (deoxy[heme]) using time-resolved (TR-) NIRS, and how these relate to slowed pulmonary V ̇O2 kinetics. 17 healthy men completed constant power tests during 1) S heavy intensity exercise; and 2) U exercise at the same absolute work rate, with a subset of 10 completing additional tests at the same relative work rate as S. Pulmonary V ̇O2 was measured breath-by-breath and, deoxy- and total[heme] were resolved via TR-NIRS in the superficial and deep vastus lateralis and superficial rectus femoris. The fundamental phase V ̇O2 time constant was increased during S compared to U (S: 36±10 vs. U: 27±8 s, P<0.001). The deoxy[heme] amplitude (S: 25-28 vs. U: 13-18 µM, P<0.05) and total[heme] amplitude (S: 17-20 vs. U: 9-16µM, P<0.05) were greater in S compared to U and were consistent for the same absolute (above data) and relative work rates (n=10, all P<0.05). The greater deoxy- and total[heme] amplitudes in S vs. U supports that reduced perfusive Q ̇O2 in S, even within deep muscle, necessitated a greater reliance on fractional O2 extraction and diffusive Q ̇O2. The slower V ̇O2 kinetics in S vs. U demonstrates that, ultimately, these adaptations were insufficient to prevent impairments in whole-body oxidative metabolism.

Item Type:	Article
Additional Information and Comments:	Copyright © 2020 the American Physiological Society. This is the author's version of an article that was accepted for publication in the Journal of Applied Physiology. The published version is available from: https://journals.physiology.org/doi/full/10.1152/japplphysiol.00213.2020
Keywords:	Time-resolved near-infrared spectroscopy, oxygen delivery, muscle deoxygenation, oxidative metabolism
Faculty / Department:	Faculty of Human and Digital Sciences > School of Health and Sport Sciences
Depositing User:	Simon Marwood
Date Deposited:	18 Nov 2020 09:27
Last Modified:	18 Nov 2020 09:27
URI:	https://hira.hope.ac.uk/id/eprint/3176

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