Glucose polymer molecular weight does not affect exogenous carbohydrate oxidation.

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.