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Glucose polymer molecular weight does not affect exogenous carbohydrate oxidation.
David S Rowlands1, Gareth A Wallis, Chris Shaw
1Institute of Food, Nutrition, and Human Health, Massey University, Wellington, New Zealand. d.s.rowlands@massey.ac.nz
Medicine and Science in Sports and Exercise
|September 24, 2005
Summary
High (HMW) and low molecular weight (LMW) glucose polymer solutions did not affect substrate oxidation rates during exercise. Carbohydrate structure, osmolality, or viscosity did not impact exogenous glucose oxidation, with oxidation limited to approximately 1.0 g/min.
Area of Science:
- Exercise Physiology
- Nutritional Biochemistry
- Sports Science
Background:
- Glucose polymer solutions are used to fuel endurance exercise.
- Previous research suggested high molecular weight (HMW) solutions might enhance glucose delivery due to faster gastric emptying.
Purpose of the Study:
- To compare the effects of high (HMW) versus low molecular weight (LMW) glucose polymer solutions on substrate oxidation during prolonged cycling exercise.
- To determine if carbohydrate molecular weight influences exogenous and endogenous substrate utilization.
Main Methods:
- Eight trained cyclists completed three 150-minute cycling trials at 64% VO2max.
- Participants ingested either HMW glucose polymer, LMW glucose polymer, or plain water.
- Substrate oxidation was measured using stable-isotope tracers and indirect calorimetry.
Main Results:
- No significant difference in exogenous carbohydrate oxidation rate between HMW and LMW solutions (P=0.89).
- Carbohydrate molecular weight did not affect endogenous carbohydrate, fat oxidation, plasma free fatty acids, lactate, or glucose concentrations.
- No serious gastrointestinal issues were reported for either glucose polymer solution.
Conclusions:
- A hypotonic HMW glucose polymer solution did not enhance exogenous or endogenous substrate oxidation compared to a LMW solution during exercise.
- Carbohydrate structure, osmolality, and viscosity do not appear to affect exogenous glucose oxidation rates.
- Ingested glucose polymers are oxidized at an average rate of approximately 1.0 g/min during exercise, regardless of molecular weight.