Preexercise carbohydrate ingestion, glucose kinetics, and muscle glycogen use: Effect of the glycemic index

M. A. Febbraio, J. Keenan, D. J. Angus, S. E. Campbell, A. P. Garnham

Research output: Contribution to journalArticleResearchpeer-review

144 Citations (Scopus)

Abstract

Eight trained men cycled at 70% peak oxygen uptake for 120 min followed by a 30-min performance cycle after ingesting either a high-glycemic index (HGI), low-glycemic index (LGI), or placebo (Con) meal 30 min before exercise. Ingestion of HGI resulted in an elevated (P < 0.01) blood glucose concentration compared with LGI and Con. At the onset of exercise, blood glucose fell (P < 0.05) such that it was lower (P < 0.05) in HGI compared with LGI and Con at 15 and 30 min during exercise. Plasma insulin concentration was higher (P < 0.01) throughout the rest period after ingestion of HGI compared with LGI and Con. Plasma free fatty acid concentrations were lower (P < 0.05) throughout exercise in HGI compared with LGI and Con. The rates of [6,6-2H]glucose appearance and disappearance were higher (P < 0.05) at rest after ingestion and throughout exercise in HGI compared with LGI and Con. Carbohydrate oxidation was higher (P < 0.05) throughout exercise, whereas glycogen use tended (P = 0.07) to be higher in HGI compared with LGI and Con. No differences were observed in work output during the performance cycle when comparing the three trials. These results demonstrate that preexercise carbohydrate feeding with a HGI, but not a LGI, meal augments carbohydrate utilization during exercise but does not effect exercise performance.

Original languageEnglish
Pages (from-to)1845-1851
Number of pages7
JournalJournal of Applied Physiology
Volume89
Issue number5
Publication statusPublished - 20 Nov 2000
Externally publishedYes

Keywords

  • Glucose production
  • Glucose uptake
  • Glycogenolysis
  • Preexercise feeding

Cite this