Goulding, Richie P and Roche, Denise and Marwood, Simon (2019) EFFECT OF HYPEROXIA ON CRITICAL POWER AND V ̇O2 KINETICS DURING UPRIGHT CYCLING. Medicine & Science in Sports & Exercise. ISSN 0195-9131 (Accepted for Publication)

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Introduction/Purpose: Critical power (CP) is a fundamental parameter defining high-intensity exercise tolerance, however its physiological determinants are incompletely understood. The present study determined the impact of hyperoxia on CP, the time constant of phase II pulmonary oxygen uptake kinetics (τ_V ̇ O2), and muscle oxygenation (assessed by near-infrared spectroscopy) in 9 healthy men performing upright cycle ergometry. Methods: CP was determined in normoxia and hyperoxia (fraction of inspired O2 = 0.5) via 4 severe-intensity constant load exercise tests to exhaustion on a cycle ergometer, repeated once in each condition. During each test, τ_V ̇ O2 and the time constant of muscle deoxyhaemoglobin kinetics (τ[HHb]), alongside absolute concentrations of muscle oxyhaemoglobin ([HbO2]), were determined. Results: CP was greater (hyperoxia: 216 ± 30 vs. normoxia: 197 ± 29W; P < 0.001) whereas W’ was reduced (hyperoxia: 15.4 ± 5.2 kJ, normoxia: 17.5 ± 4.3 W; P = 0.037) in hyperoxia compared to normoxia. τ_V ̇ O2 (hyperoxia: 35 ± 12 vs normoxia: 33 ± 10 s; P = 0.33) and τ[HHb] (hyperoxia: 11 ± 5 vs. normoxia: 14 ± 5 s; P = 0.65) were unchanged between conditions, whereas [HbO2] during exercise was greater in hyperoxia compared to normoxia (hyperoxia: 73 ± 20 vs. normoxia: 66 ± 15 μM; P = 0.001). Conclusion: This study provides novel insights into the physiological determinants of CP and by extension, exercise tolerance. Microvascular oxygenation and CP were improved during exercise in hyperoxia compared with normoxia. Importantly, the improved microvascular oxygenation afforded by hyperoxia did not alter τ_V ̇ O2, suggesting that microvascular O2 availability is an independent determinant of the upper limit for steady-state exercise, i.e. CP.

Item Type: Article
Additional Information and Comments: This is the author's version of an article that was accepted for publication in Medicine & Science in Sports & Exercise. The journal is published online at https://journals.lww.com/acsm-msse/pages/default.aspx
Keywords: critical power, exercise tolerance, oxidative metabolism, oxygen uptake kinetics, power-duration relationship, hyperoxia
Faculty / Department: Faculty of Science > School of Health Sciences
Depositing User: Simon Marwood
Date Deposited: 13 Dec 2019 14:15
Last Modified: 13 Dec 2019 14:15
URI: https://hira.hope.ac.uk/id/eprint/2987

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