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Carbohydrate dependence during prolonged simulated cycling time trials.

Samuel L Torrens¹, José L Areta², Evelyn B Parr¹

¹Mary MacKillop Institute for Health Research, Centre for Exercise and Nutrition, Australian Catholic University, Melbourne, VIC, 3065, Australia.

European Journal of Applied Physiology

|February 7, 2016

Summary

Nicotinic acid (NA) impaired 120-minute cycling performance by suppressing fat utilization. Carbohydrate (CHO) remains the primary fuel source for endurance cycling, with some lipid use also observed.

Keywords:

Fat High-intensity cycling Nicotinic acid Performance Substrate utilisation

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Area of Science:

Exercise Physiology
Nutritional Biochemistry

Background:

Endurance exercise relies on substrate utilization for performance.
Lipolysis, the breakdown of fats, is a key energy pathway during prolonged exercise.

Purpose of the Study:

To investigate the impact of suppressing lipolysis with Nicotinic acid (NA) and pre-exercise carbohydrate (CHO) feeding on substrate utilization and cycling time trial (TT) performance.
To determine if inhibiting fat metabolism affects endurance performance in trained cyclists.

Main Methods:

A randomized, single-blind, crossover study involving eight trained male cyclists/triathletes.
Participants completed 60, 90, and 120-minute cycling time trials (TTs) after a standardized CHO breakfast and ingestion of either NA or placebo (PL).

Main Results:

Nicotinic acid (NA) successfully suppressed plasma free fatty acids, indicating reduced lipolysis.
Cycling TT performance was not affected for 60- and 90-minute durations.
However, the 120-minute TT was significantly slower with NA, coinciding with a drop in plasma glucose.

Conclusions:

Nicotinic acid (NA) impairs cycling performance in longer-duration (120 min) time trials.
Endurance cycling performance lasting 60-120 minutes is highly dependent on carbohydrate (CHO) utilization.
Lipid-based fuels are utilized to some extent even during shorter endurance cycling events (1-2 hours).