File(s) under permanent embargo
Muscle metabolites and performance during high-intensity, intermittent exercise
journal contribution
posted on 1998-05-01, 00:00 authored by M Hargreaves, M J McKenna, D G Jenkins, Stuart WarmingtonStuart Warmington, J L Li, Rod SnowRod Snow, M A FebbraioSix 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 physiologyVolume
84Issue
5Pagination
1687 - 1691Publisher
American Physiological SocietyLocation
Bethesda, Md.ISSN
8750-7587eISSN
0161-7567Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
1998, the American Physiological SocietyUsage metrics
Categories
No categories selectedKeywords
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC