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



Davies, Matthew J, Benson, Alan P, Cannon, Daniel T, Marwood, Simon, Kemp, Graham J ORCID: 0000-0002-8324-9666, Rossiter, Harry B and Ferguson, Carrie
(2017) Dissociating external power from intramuscular exercise intensity during intermittent bilateral knee-extension in humans. Journal of Physiology, 595 (21). 6673 - 6686.

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Abstract

Compared with work‐matched high‐intensity continuous exercise, intermittent exercise dissociates pulmonary oxygen uptake (urn:x-wiley:00223751:media:tjp12540:tjp12540-math-0004) 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, whereas peak urn:x-wiley:00223751:media:tjp12540:tjp12540-math-0005 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 urn:x-wiley:00223751:media:tjp12540:tjp12540-math-0006 compared to 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 and 64:128 s). Target work duration (576 s) was achieved in all intermittent protocols; greater than continuous (252 ± 174 s; P < 0.05). Mean ATP turnover rate was not different between protocols (∼43 mm min−1 on average). However, the intramuscular phosphocreatine (PCr) component of ATP generation was greatest (∼30 mm min−1), and oxidative (∼10 mm min−1) and anaerobic glycolytic (∼1 mm min−1) components were lowest for 16:32 and 32:64 s intermittent protocols, compared to 64:128 s (18 ± 6, 21 ± 10 and 10 ± 4 mm min−1, respectively) and continuous protocols (8 ± 6, 20 ± 9 and 16 ± 14 mm min−1, respectively). As intermittent work duration increased towards continuous exercise, 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 urn:x-wiley:00223751:media:tjp12540:tjp12540-math-0007 and intramuscular metabolism, dissociating exercise intensity from the power output and work done.

Item Type: Article
Uncontrolled Keywords: bioenergetics, exercise intensity, exercise tolerance, interval exercise
Depositing User: Symplectic Admin
Date Deposited: 15 Aug 2017 06:51
Last Modified: 07 Jun 2022 19:10
DOI: 10.1113/JP274589
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3008973