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Metabolic Changes in Single Human Muscle Fibres During Brief Maximal Exercise
Author(s) -
Karatzaferi C.,
Haan A.,
Mechelen W.,
Sargeant A. J.
Publication year - 2001
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/eph8602223
Subject(s) - phosphocreatine , myosin , inosine monophosphate , creatine , vastus lateralis muscle , medicine , skeletal muscle , endocrinology , fibre type , chemistry , gene isoform , fast twitch muscle , carnitine , energy metabolism , biochemistry , biology , nucleotide , gene
Changes in high‐energy phosphate levels in single human skeletal muscle fibres after 10 s of maximal (all‐out) dynamic exercise were investigated. Muscle biopsies from vastus lateralis of two volunteers were collected at rest and immediately post exercise. Single muscle fibres were dissected from dry muscle and were assigned into one of four groups according to their myosin heavy chain (MyHC) isoform content: that is type I, IIA, IIAx and IIXa (the latter two groups containing either less or more than 50% IIX MyHC). Fragments of characterised fibres were analysed by HPLC for ATP, inosine‐monophosphate (IMP), phosphocreatine (PCr) and creatine levels. After 10 s of exercise, PCr content ([PCr]) declined by approximately 46, 53, 62 and 59% in type I, IIA, IIAx and IIXa fibres, respectively ( P < 0.01 from rest). [ATP] declined only in type II fibres, especially in IIAx and IIXa fibres in which [IMP] reached mean values of 16 ± 1 and 18 ± 4 mmol (kg dry mass) −1 , respectively. While [PCr] was reduced in all fibre types during the brief maximal dynamic exercise, it was apparent that type II fibres expressing the IIX myosin heavy chain isoform were under a greatest metabolic stress as indicated by the reductions in [ATP].