title: Effect of a 2-h hyperglycemic-hyperinsulinemic glucose clamp to promote glucose storage on endurance exercise performance.
abstract: Carbohydrate stores within muscle are considered essential as a fuel for prolonged endurance exercise, and regimes for enhancing such stores have proved successful in aiding performance. This study explored the effects of a hyperglycaemic-hyperinsulinemic clamp performed 18 h previously on subsequent prolonged endurance performance in cycling. Seven male subjects, accustomed to prolonged endurance cycling, performed 90 min of cycling at ~65% VO(2max) followed by a 16-km time trial 18 h after a 2-h hyperglycemic-hyperinsulinemic clamp (HCC). Hyperglycemia (10 mM) with insulin infused at 300 mU/m(2)/min over a 2-h period resulted in a total glucose uptake of 275 g (assessed by the area under the curve) of which glucose storage accounted for about 73% (i.e. 198 g). Patterns of substrate oxidation during 90-min exercise at 65% VO(2max) were not altered by HCC. Blood glucose and plasma insulin concentrations were higher during exercise after HCC compared with control (p < 0.05) while plasma NEFA was similar. Exercise performance was improved by 49 s and power output was 10-11% higher during the time trial (p < 0.05) after HCC. These data suggest that carbohydrate loading 18 h previously by means of a 2-h HCC improves cycling performance by 3.3% without any change in pattern of substrate oxidation.
authors.affiliation: Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Henry Cotton Campus, Webster Street, Liverpool, L3 2ET, UK. d.p.maclaren@ljmu.ac.uk
authors.forename: D P M
authors.initials: DP
authors.lastname: Maclaren
authors.forename: H
authors.initials: H
authors.lastname: Mohebbi
authors.forename: M
authors.initials: M
authors.lastname: Nirmalan
authors.forename: M A
authors.initials: MA
authors.lastname: Keegan
authors.forename: C T
authors.initials: CT
authors.lastname: Best
authors.forename: D
authors.initials: D
authors.lastname: Perera
authors.forename: M N
authors.initials: MN
authors.lastname: Harvie
authors.forename: I T
authors.initials: IT
authors.lastname: Campbell
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology*; D015309:Glucose Clamp Technique / Q000379:methods; D006801:Humans; D006943:Hyperglycemia / Q000097:blood; D006946:Hyperinsulinism / Q000097:blood; D007328:Insulin / Q000097:blood; D008297:Male; D010807:Physical Endurance / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005947:Glucose