Journal of Applied Physiology
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J Appl Physiol 87: 116-123, 1999;
8750-7587/99 $5.00
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Vol. 87, Issue 1, 116-123, July 1999

Effects of creatine supplementation on the energy cost of muscle contraction: a 31P-MRS study

Sinclair A. Smith1, Scott J. Montain2, Ralph P. Matott2, Gary P. Zientara3, Ferenc A. Jolesz3, and Roger A. Fielding1

1 Department of Health Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston 02215; 2 United States Army Research Institute of Environmental Medicine, Natick 01760; and 3 Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115

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. 31P spectra were used to determine pH and relative concentrations of Pi, phosphocreatine (PCr), and beta ATP. 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 Delta PCr 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 (Delta ATP/N) and dynamic (Delta ATP/J) costs of contraction were unaffected by creatine supplementation as well as were ATP, Pi, pH, PCr resynthesis rate, and muscle strength and endurance. Delta ATP/J and Delta ATP/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.

muscle economy; phosphocreatine; skeletal muscle; magnetic resonance spectroscopy


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