Dissociating external power from intramuscular exercise intensity during intermittent bilateral knee-extension in humans

Davies, Matthew J and Benson, Alan P and Cannon, Daniel T and Marwood, Simon and Kemp, Graham J. and Rossiter, Harry B and Ferguson, Carrie (2017) Dissociating external power from intramuscular exercise intensity during intermittent bilateral knee-extension in humans. Journal of Physiology. ISSN 1469-7793

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Abstract

Compared with work-matched high-intensity continuous exercise, intermittent exercise dissociates pulmonary oxygen uptake (V̇O2) from the accumulated work. The extent to which this reflects differences in O2 storage fluctuations and/or contributions from oxidative and substrate-level bioenergetics is unknown. Using pulmonary gas-exchange and intramuscular 31P magnetic resonance spectroscopy, we tested the hypotheses that at the same power: ATP synthesis rates are similar; but peak V̇O2 amplitude is lower in intermittent vs. continuous exercise. Thus, we expected that: intermittent exercise relies less upon anaerobic glycolysis for ATP provision than continuous exercise; shorter intervals would require relatively greater fluctuations in intramuscular bioenergetics than in V̇O2 compared with longer intervals. Six men performed bilateral knee-extensor exercise (estimated to require 110% peak aerobic power) continuously and with three different intermittent work:recovery durations (16:32; 32:64; 64:128s). Target work duration (576s) was achieved in all intermittent protocols; greater than continuous (252±174s; p<0.05). Mean ATP turnover rate was not different between protocols (~43mM·min-1 on average). However, the intramuscular PCr component of ATP generation was greatest (~30mM·min-1), and oxidative (~10mM·min-1) and anaerobic glycolytic (~1mM·min-1) components lowest for 16:32 and 32:64s intermittent protocols, compared with 64:128s (18±6, 21±10 and 10±4mM·min-1, respectively) and continuous protocols (8±6, 20±9 and 16±14mM·min-1, respectively). As intermittent work duration increased towards continuous, ATP production relied proportionally more upon anaerobic glycolysis and oxidative phosphorylation, and less upon PCr breakdown. However, performing the same high-intensity power intermittently vs. continuously reduced the amplitude of fluctuations in V̇O2 and intramuscular metabolism, dissociating exercise intensity from the power output and work done.

Item Type: Article
Additional Information and Comments: This is the peer reviewed version of the following article: Davies, M. J., Benson, A. P., Cannon, D. T., Marwood, S., Kemp, G. J., Rossiter, H. B. and Ferguson, C. (2017), Dissociating external power from intramuscular exercise intensity during intermittent bilateral knee-extension in humans, Journal of Physiology, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1113/JP274589/full This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Faculty / Department: Faculty of Science > School of Health Sciences
Depositing User: Simon Marwood
Date Deposited: 18 Sep 2017 15:34
Last Modified: 18 Sep 2017 15:34
URI: http://hira.hope.ac.uk/id/eprint/2142

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