Effect of creatine supplementation and resistance-exercise training on muscle insulin-like growth factor in young adults.
The purpose of this study was to compare changes in muscle insulin-like growth factor-I (IGF-I) content resulting from resistance-exercise training (RET) and creatine supplementation (CR). Male (n=24) and female (n=18) participants with minimal resistance-exercise-training experience (=1 year) who were participating in at least 30 min of structured physical activity (i.e., walking, jogging, cycling) 3-5 x/wk volunteered for the study. Participants were randomly assigned in blocks (gender) to supplement with creatine (CR: 0.25 g/kg lean-tissue mass for 7 days; 0.06 g/kg lean-tissue mass for 49 days; n=22, 12 males, 10 female) or isocaloric placebo (PL: n=20, 12 male, 8 female) and engage in a whole-body RET program for 8 wk. Eighteen participants were classified as vegetarian (lacto-ovo or vegan; CR: 5 male, 5 female; PL: 3 male, 5 female). Muscle biopsies (vastus lateralis) were taken before and after the intervention and analyzed for IGF-I using standard immunohistochemical procedures. Stained muscle cross-sections were examined microscopically and IGF-I content quantified using image-analysis software. Results showed that RET increased intramuscular IGF-I content by 67%, with greater accumulation from CR (+78%) than PL (+54%; p=.06). There were no differences in IGF-I between vegetarians and nonvegetarians. These findings indicate that creatine supplementation during resistance-exercise training increases intramuscular IGF-I concentration in healthy men and women, independent of habitual dietary routine.
Burke
Darren G
DG
Department of Human Kinetics, St. Francis Xavier University, Antigonish, NS, Canada.
Candow
Darren G
DG
Chilibeck
Philip D
PD
MacNeil
Lauren G
LG
Roy
Brian D
BD
Tarnopolsky
Mark A
MA
Ziegenfuss
Tim
T
D000328:Adult; D003401:Creatine / Q000008:administration & dosage* / Q000032:analysis; D014676:Diet, Vegetarian; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D014891:Weight Lifting / Q000502:physiology*
D007334:Insulin-Like Growth Factor I; D003401:Creatine