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8083765 
Journal Article 
Noninvasive measurement of phosphocreatine recovery kinetics in single human muscles 
Walter, G; Vandenborne, K; Mccully, KK; Leigh, JS 
1997 
Yes 
American Journal of Physiology: Cell Physiology
ISSN: 0363-6143
EISSN: 1522-1563 
AMER PHYSIOLOGICAL SOC 
BETHESDA 
272 
2 
C525-C534 
English 
9124295 
WOS:A1997WJ63300019 
The rate at which phosphocreatine (PCr) is resynthesized after exercise is related to muscle oxidative capacity (V(max)). With the use of a one- dimensional image-guided, localized nuclear magnetic resonance spectroscopy technique, PCr kinetics were monitored in the medial gastrocnemius of eight healthy subjects after voluntary, short duration, maximal rate exercise. Localized spectra were obtained every 6 s with <5% contamination from nonselected regions. Maximal rate exercise elicited near-maximal to maximal muscle activation, as indicated by the high-PCr hydrolysis rate (2.26 ± 0.07 mM/s) and extensive PCr depletion. At the end of 9 s of maximal rate exercise, PCr was depleted by 61.4 ± 2.4% and intracellular pH was 7.04 ± 0.03. After 9 s of maximal rate exercise, PCr recovered with a rate constant (k(PCr)) of 1.87 ± 0.15 min-1 and a V(max) of 67.2 ± 6.0 mM/min. Independent of prior activity, aerobic ATP synthesis rates reached 48.6 ± 4.9 mM/min within 9 s. Extending maximal rate exercise to 30 s resulted in 92.0 ± 1.2% PCr depletion and an intracellular pH of 6.45 ± 0.07. The intracellular acidosis separated the direct relationship between k(Pcr) and muscle V(max) but did not affect the initial PCr resynthesis rate. 
phosphorus-31 magnetic resonance spectroscopy; skeletal muscle; muscle energetics; muscle metabolism; exercise