Effects of creatine supplementation on the energy cost of muscle contraction: a 31P-MRS study.
Five women and 3 men (29.8 +/- 1.4 yr) performed dynamic knee-extension exercise inside a magnetic resonance system (means +/- SE). Two trials were performed 7-14 days apart, consisting of a 4- to 5-min exhaustive exercise bout. To determine quadriceps cost of contraction, brief static and dynamic contractions were performed pre- and postexercise. (31)P spectra were used to determine pH and relative concentrations of P(i), phosphocreatine (PCr), and betaATP. Subjects consumed 0.3 g. kg(-1). day(-1) of a placebo (trial 1) or creatine (trial 2) for 5 days before each trial. After creatine supplementation, resting DeltaPCr increased from 40.7 +/- 1.8 to 46. 6 +/- 1.1 mmol/kg (P = 0.04) and PCr during exercise declined from -29.6 +/- 2.4 to -34.1 +/- 2.8 mmol/kg (P = 0.02). Muscle static (DeltaATP/N) and dynamic (DeltaATP/J) costs of contraction were unaffected by creatine supplementation as well as were ATP, P(i), pH, PCr resynthesis rate, and muscle strength and endurance. DeltaATP/J and DeltaATP/N were greatest at the onset of the exercise protocol (P < 0.01). In summary, creatine supplementation increased muscle PCr concentration, which did not affect muscle ATP cost of contraction.
Smith
S A
SA
Department of Health Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, Massachusetts 02215, USA. smiths@mail.belmont.edu
Montain
S J
SJ
Matott
R P
RP
Zientara
G P
GP
Jolesz
F A
FA
Fielding
R A
RA
D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D003401:Creatine / Q000008:administration & dosage*; D004734:Energy Metabolism / Q000187:drug effects; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D010758:Phosphorus; D010807:Physical Endurance / Q000187:drug effects / Q000502:physiology
D010710:Phosphates; D010725:Phosphocreatine; D010758:Phosphorus; D000255:Adenosine Triphosphate; D003401:Creatine