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Muscle metabolites and performance during high-intensity, intermittent exercise

Version 2 2024-06-03, 10:43
Version 1 2015-11-13, 15:44
journal contribution
posted on 2024-06-03, 10:43 authored by M Hargreaves, MJ McKenna, DG Jenkins, Stuart WarmingtonStuart Warmington, JL Li, Rod SnowRod Snow, MA Febbraio
Six men were studied during four 30-s ‘‘all-out’’ exercise bouts on an air-braked cycle ergometer. The first three exercise bouts were separated by 4 min of passive recovery; after the third bout, subjects rested for 4 min, exercised for 30 min at 30–35% peak O2 consumption, and rested for a further 60 min before completing the fourth exercise bout. Peak power and total work were reduced (P < 0.05) during bout 3 [765 ± 60 (SE)W; 15.8 ± 1.0 kJ] compared with bout 1 (1,686 ± 55 W, 23.8 ± 1.2 kJ), but no difference in exercise performance was observed between bouts 1 and 4 (1,094 ± 64 W, 23.2 ± 1.4 kJ). Before bout 3, muscle ATP, creatine phosphate (CP), glycogen, pH, and sarcoplasmic reticulum (SR) Ca2+ uptake were reduced, while muscle lactate and inosine 58-monophosphate were increased. Muscle ATP and glycogen before bout 4 remained lower than values before bout 1 (P < 0.05), but there were no differences in muscle inosine 58-monophosphate, lactate, pH, and SR Ca2+ uptake. Muscle CP levels before bout 4 had increased above resting levels. Consistent with the decline in muscle ATP were increases in hypoxanthine and inosine before bouts 3 and 4. The decline in exercise performance does not appear to be related to a reduction in muscle glycogen. Instead, it may be caused by reduced CP availability, increased H+ concentration, impairment in SR function, or some other fatigue-inducing agent.

History

Journal

Journal of applied physiology

Volume

84

Pagination

1687-1691

Location

Bethesda, Md.

ISSN

8750-7587

eISSN

0161-7567

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

1998, the American Physiological Society

Issue

5

Publisher

American Physiological Society

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