Muscle metabolites and performance during high-intensity, intermittent exercise

• Published in: Journal of applied physiology (1985) Vol. 84; no. 5; pp. 1687 - 1691
• Main Authors: Hargreaves, Mark, McKenna, Michael J, Jenkins, David G, Warmington, Stuart A, Li, Jia L, Snow, Rodney J, Febbraio, Mark A
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.05.1998; American Physiological Society
• Subjects: Adenosine Triphosphate - analysis; Adenosine Triphosphate - metabolism; Adult; Biological and medical sciences; Biopsy; Calcium - metabolism; Ergometry; Fundamental and applied biological sciences. Psychology; Glycogen - metabolism; Humans; Hydrogen-Ion Concentration; Hypoxanthine - metabolism; Inosine Monophosphate - metabolism; Lactic Acid - metabolism; Male; Muscles - metabolism; Oxygen Consumption - physiology; Phosphocreatine - metabolism; Physical Exertion - physiology; Sarcoplasmic Reticulum - physiology; Space life sciences; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; Physical exercise; Human; Energy metabolism; Calcium; Excitation contraction coupling; Glycogen; Intermittent; Sarcoplasmic reticulum; Intensity; Bicycle ergometer; Phosphocreatine; Striated muscle
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1998.84.5.1687

1  Department of Physiology, The University of Melbourne, Parkville 3052; 2  Department of Human Movement, Recreation, and Performance, and 3  Exercise Metabolism Unit, Department of Chemistry and Biology, Centre for Rehabilitation, Exercise, and Sport Science, Victoria University of Technology, Footscray 3011; and 4  Department of Human Movement Studies, The University of Queensland, Brisbane 4072, Australia 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 O 2 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  (1,168 ± 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) Ca 2+ uptake were reduced, while muscle lactate and inosine 5'-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 5'-monophosphate, lactate, pH, and SR Ca 2+ 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. muscle fatigue; metabolism; glycogen; creatine phosphate; hydrogen ion