This meticulous and careful research was carried out by Christina Karatzaferi as part of her PhD working under the supervision of Professor Anthony J Sargeant. The results confirm and validate previous published work and speculation by Tony Sargeant in 1987 (published in the Journal of Applied Physiology) showing the time course of the recovery of high energy phosphate levels in human muscle following maximum sprint exercise. In the 1987 paper it was impossible at that time to measure the PCr and ATP levels in single fibres and the conclusions were based on recovery of muscle power. The present paper was able to link this to a metabolic cause, that is the dependence upon the replenishment of the high energy phosphates in the muscle.
Phosphocreatine and ATP content in human single muscle fibres before and after maximum dynamic exercise
Pfluegers Arch. 2001 Jun;442(3):467-74
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