Elevated baseline work rate slows pulmonary oxygen uptake kinetics and decreases critical power during upright cycle exercise

Goulding, Richie P and Roche, Denise and Marwood, Simon (2018) Elevated baseline work rate slows pulmonary oxygen uptake kinetics and decreases critical power during upright cycle exercise. Physiological Reports, 6 (14). ISSN 2051-817X (Accepted for Publication)

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Critical power is a fundamental parameter defining high-intensity exercise tolerance, and is related to the phase II time constant of pulmonary oxygen uptake kinetics (O2). Whether this relationship is causative is presently unclear. The present study determined the impact of raised baseline work rate, which increases O2, on critical power during upright cycle exercise. Critical power was determined via four constant-power exercise tests to exhaustion in two conditions: 1) with exercise initiated from an unloaded cycling baseline (U→S), and 2) with exercise initiated from a baseline work rate of 90% of the gas exchange threshold (M→S). During these exercise transitions, O2 and the time constant of muscle deoxyhaemoglobin kinetics (τ[HHb + Mb]) (the latter via near-infrared spectroscopy) were determined. In M→S, critical power was lower (M→S = 203 ± 44 W vs. U→S = 213 ± 45 W, P = 0.011) and O2 was greater (M→S = 51 ± 14 s vs. U→S = 34 ± 16 s, P = 0.002) when compared to U→S. Additionally, τ[HHb + Mb] was greater in M→S compared to U→S (M→S = 28 ± 7 s vs. U→S = 14 ± 7 s, P = 0.007). The increase inO2 and concomitant reduction in critical power inM→S compared to U→S suggests a causal relationship between these two parameters. However, that τ[HHb + Mb] was greater in M→S exculpates reduced oxygen availability as being a confounding factor. These data therefore provide the first experimental evidence that O2 is an independent determinant of critical power. Keywords critical power, exercise tolerance, oxygen uptake kinetics, power-duration relationship, muscle deoxyhaemoglobin kinetics, work-to-work exercise.

Item Type: Article
Additional Information and Comments: This is the peer-reviewed version of an article that has been accepted for publication in Physiological Reports. The final, published version is available at https://physoc.onlinelibrary.wiley.com/doi/full/10.14814/phy2.13802
Keywords: exercise tolerance, critical power, oxygen uptake kinetics, work-to-work exercise, near infrared spectroscopy
Faculty / Department: Faculty of Science > School of Health Sciences
Depositing User: Simon Marwood
Date Deposited: 04 Jul 2018 09:26
Last Modified: 09 May 2019 15:05
URI: https://hira.hope.ac.uk/id/eprint/2560

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