Creatine Supplementation And Age Influence Muscle Metabolism During Exercise

[vindiesel]

Creatine supplementation and age influence muscle metabolism during exercise.

Smith SA, Montain SJ, Matott RP, Zientara GP, Jolesz FA, Fielding RA.

Department of Health Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, 02215, Massachusetts, USA.

Young [n = 5, 30 +/- 5 (SD) yr] and middle-aged (n = 4, 58 +/- 4 yr) men and women performed single-leg knee-extension exercise inside a whole body magnetic resonance system. Two trials were performed 7 days apart and consisted of two 2-min bouts and a third bout continued to exhaustion, all separated by 3 min of recovery. 31P spectra were used to determine pH and relative concentrations of Pi, phosphocreatine (PCr), and beta-ATP every 10 s. The subjects consumed 0.3 g . kg-1 . day-1 of a placebo (trial 1) or creatine (trial 2) for 5 days before each trial. During the placebo trial, the middle-aged group had a lower resting PCr compared with the young group (35.0 +/- 5.2 vs. 39.5 +/- 5.1 mmol/kg, P < 0.05) and a lower mean initial PCr resynthesis rate (18.1 +/- 3.5 vs. 23.2 +/- 6.0 mmol . kg-1 . min-1, P < 0.05). After creatine supplementation, resting PCr increased 15% (P < 0.05) in the young group and 30% (P < 0.05) in the middle-aged group to 45.7 +/- 7.5 vs. 45.7 +/- 5.5 mmol/kg, respectively. Mean initial PCr resynthesis rate also increased in the middle-aged group (P < 0.05) to a level not different from the young group (24.3 +/- 3.8 vs. 24.2 +/- 3.2 mmol . kg-1 . min-1). Time to exhaustion was increased in both groups combined after creatine supplementation (118 +/- 34 vs. 154 +/- 70 s, P < 0.05). In conclusion, creatine supplementation has a greater effect on PCr availability and resynthesis rate in middle-aged compared with younger persons.

PMID: 9760327 [PubMed - indexed for MEDLINE]