Non-P(i) buffer capacity and initial phosphocreatine breakdown and resynthesis kinetics of human gastrocnemius/soleus muscle groups using 0.5 s time-resolved (31)P MRS at 4.1 T

NMR Biomed. 1999 Dec;12(8):545-51. doi: 10.1002/(sici)1099-1492(199912)12:8<545::aid-nbm595>;2-j.


High-time-resolution (0.5 s) (31)P MRS has been used to evaluate the initial phosphoreatine (PCr) breakdown and resynthesis kinetics, to calculate the non-P(i)(/non-bicarbonate) buffer capacity (betanon-P(i)(/non-bicarb)), and to calculate the constant relating the change in intracellular pH to the muscle's H(+) efflux rate (lambda). The slope of PCr vs time demonstrates that a slope calculated using the first 10 s of recovery underestimates initial PCr recovery rates by up to 56%. A 1-2 s time window is needed to produce a slope that is statistically equivalent to the slope measured using a 0.5 s time window (p = 0.008, one-way RM-ANOVA, Student-Newman-Keuls multiple comparison test). In addition, there was no delay or acceleration in PCr recovery after a 90 s maximum voluntary contraction (MVC) in normal subjects. This demonstrates that oxidative metabolism is occurring at the end of a 90-s MVC in normal individuals. Fitting recovery data has determined that betanon-P(i)(/non-bicarb) = 24.3 +/- 5.4 slyke (mmol/L/pH unit) and that lambda = 0.129 +/- 0.077 mM/(ph s) for human gastrocnemius/soleus muscle. betanon-P(i)(/non-bicarb) is in agreement with measurements in cat biceps, cat soleus and rat gastrocnemius muscles.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Buffers
  • Humans
  • Kinetics
  • Magnetic Resonance Spectroscopy
  • Muscles / metabolism*
  • Phosphocreatine / metabolism*


  • Buffers
  • Phosphocreatine