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Glucose polymer molecular weight does not affect exogenous carbohydrate oxidation

journal contribution
posted on 2005-09-01, 00:00 authored by D S Rowlands, G A Wallis, Chris ShawChris Shaw, R L P G Jentjens, A E Jeukendrup
PURPOSE: To compare the effects of high (HMW) versus low molecular weight (LMW) glucose polymer solutions on the pattern of substrate oxidation during exercise. METHODS: Eight cyclists (VO(2max): 63 +/- 8 mL.kg(-1).min(-1)) performed three 150-min cycling trials at 64 +/- 5% VO(2max) while ingesting 11.25% HMW (500-750 kg.mol(-1), 21 mOsm.kg(-1)) or LMW (8 kg.mol(-1), 110 mOsm.kg(-1)) solutions providing 1.8 g of carbohydrate per minute, or plain water. Substrate oxidation was determined using stable-isotope methods and indirect calorimetry. RESULTS: Exogenous carbohydrate oxidation rate was not affected by carbohydrate molecular weight (P = 0.89, peak rate: 0.93 x// 1.37 g.min(-1)). There was no effect of carbohydrate molecular weight on endogenous carbohydrate or fat oxidation rates (P = 0.30), plasma free fatty acid (P = 0.14), lactate (P = 0.38), or glucose concentrations (P = 0.98), nor were there any serious gastrointestinal complaints reported for either of the two solutions during exercise. CONCLUSIONS: Despite previous reports of faster gastric emptying and glycogen resynthesis suggesting enhanced glucose delivery, a markedly hypotonic HMW glucose polymer solution had no effect on exogenous and endogenous substrate oxidation rates during exercise, relative to a LMW glucose polymer solution. These data are consistent with there being no effect of carbohydrate structure or solution osmolality or viscosity on exogenous glucose oxidation and that ingested glucose polymers can only be oxidized on average up to 1.0 g.min during exercise.

History

Journal

Medicine and science in sports and exercise

Volume

37

Issue

9

Pagination

1510 - 1516

Publisher

Lippincott, Williams & Wilkins

Location

Philadelphia, Pa.

ISSN

0195-9131

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2005, American College of Sports Medicine