title: Phosphocreatine and ATP content in human single muscle fibres before and after maximum dynamic exercise.
abstract: The recovery of high-energy phosphate levels in single human skeletal muscle fibres following short-term maximal (all-out) exercise was investigated. Three male volunteers exercised maximally for 25 s on an isokinetic cycling ergometer. Muscle biopsy samples from the vastus lateralis were collected at rest, immediately post-exercise and at 1.5 min of recovery. The subjects also performed a second exercise bout 1.5 min after the first, on a separate occasion. Single muscle fibres were dissected, characterized and assigned to one of four groups according to their myosin heavy chain (MyHC) isoform content; namely, type I, IIA, IIAx and IIXa (the latter two groups containing either less or more than 50% IIX MyHC). Fibres were analysed for adenosine 5'-triphosphate (ATP), inosine-5'-monophosphate (IMP), phosphocreatine (PCr) and creatine (Cr) levels. Type I fibres had a lower Cr content than type II fibres (P<0.01). Within type II fibres resting [PCr] increased with increasing MyHC IIX isoform content (r=0.59, P<0.01). Post-exercise [PCr] was very low in all fibre groups (P<0.01 versus rest) while great reductions in ATP were also observed (P<0.01 versus rest), especially in the type II fibre groups. [PCr] at 1.5 min of recovery was still lower compared to rest for all fibre groups (P<0.01) especially in the IIAx and IIXa fibres.
authors.affiliation: Neuromuscular Biology Research Group, Manchester Metropolitan University, UK. C.Karatzaferi@ed.ac.uk
authors.forename: C
authors.initials: C
authors.lastname: Karatzaferi
authors.forename: A
authors.initials: A
authors.lastname: de Haan
authors.forename: R A
authors.initials: RA
authors.lastname: Ferguson
authors.forename: W
authors.initials: W
authors.lastname: van Mechelen
authors.forename: A J
authors.initials: AJ
authors.lastname: Sargeant
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D005080:Exercise Test; D006801:Humans; D007291:Inosine Monophosphate / Q000378:metabolism; D007536:Isomerism; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000032:analysis / Q000737:chemistry; D010725:Phosphocreatine / Q000378:metabolism*; D005082:Physical Exertion / Q000502:physiology
chemical_list: D010725:Phosphocreatine; D007291:Inosine Monophosphate; D000255:Adenosine Triphosphate; D018995:Myosin Heavy Chains