No Effects of Carbohydrate Ingestion on Muscle Metabolism or Performance During Short-Duration High-Intensity...

Area of Science:

• Exercise Physiology
• Sports Nutrition
• Metabolic Responses to Exercise

Background:

• Carbohydrates are vital for high-intensity exercise.
• The role of carbohydrate supplementation in short-duration, high-intensity intermittent exercise is not fully understood.
• This study investigates carbohydrate's impact on muscle metabolism and performance in this specific exercise type.

Purpose of the Study:

• To examine the effects of carbohydrate (CHO) versus placebo (PLA) supplementation on muscle glycogen metabolism and repeated sprint ability.
• To assess muscle and blood glucose and insulin responses during high-intensity intermittent exercise.
• To determine if CHO supplementation enhances performance in this exercise modality.

Main Methods:

• Randomized, counterbalanced, double-blinded crossover study with 11 trained males.
• Participants performed three high-intensity intermittent cycling exercise periods (10 x 45s at ~105% Wmax).
• Muscle biopsies and repeated sprint ability tests were conducted, alongside blood glucose and insulin measurements.

Main Results:

• No significant differences in whole-muscle or fiber-type-specific muscle glycogen degradation between CHO and PLA conditions.
• Repeated sprint ability declined similarly in both groups (~9%) after exercise.
• Despite higher blood glucose and insulin levels with CHO, performance and muscle glycogen use were unaffected.

Conclusions:

• Carbohydrate ingestion did not influence net muscle glycogen breakdown during short-duration high-intensity intermittent exercise.
• Sprint performance and perceived exertion were not enhanced by carbohydrate supplementation.
• These findings challenge the effectiveness of carbohydrate supplementation for improving performance in high-intensity intermittent sports.