Carbohydrate ingestion immediately before exercise does not improve 20 km time trial performance in well trained...

Area of Science:

• Sports Science
• Exercise Physiology
• Nutritional Science

Background:

• Carbohydrate (CHO) ingestion is a common strategy to fuel endurance exercise.
• The role of CHO availability in limiting high-intensity exercise performance is debated.
• Understanding CHO's impact on performance is crucial for athletes and coaches.

Purpose of the Study:

• To investigate the effect of a moderate carbohydrate dose on 20 km cycling time-trial performance.
• To determine if carbohydrate availability limits maximal exercise performance of approximately 30 minutes.

Main Methods:

• 14 well-trained cyclists completed two randomized 20 km cycling time-trials.
• Subjects ingested either a carbohydrate-electrolyte beverage (approx. 40g CHO) or a placebo 10 minutes before exercise.
• Performance was assessed via time to completion, with power output and heart rate monitored.

Main Results:

• No significant difference in average power output or heart rate between carbohydrate and placebo trials.
• Cycling time-trial performance times were identical for both conditions (27:41 min:sec).
• Ingested carbohydrate did not lead to improved performance in this exercise bout.

Conclusions:

• Ingestion of approximately 40g of carbohydrate does not enhance maximal cycling performance lasting around 30 minutes.
• Carbohydrate availability, indicated by circulating blood glucose, does not appear to be a limiting factor for high-intensity exercise of this duration.
• These findings challenge the necessity of pre-exercise carbohydrate intake for shorter, high-intensity cycling events.