Carbohydrate supplementation spares muscle glycogen during variable-intensity exercise

Area of Science:

• Exercise Physiology
• Sports Nutrition
• Metabolic Studies

Background:

• Muscle glycogen is a primary fuel source during prolonged exercise.
• Carbohydrate (CHO) supplementation is a common strategy to enhance endurance performance.
• Understanding CHO utilization and its impact on endurance is crucial for athletes.

Purpose of the Study:

• To evaluate the effects of liquid (L) and solid (S) carbohydrate supplementation on muscle glycogen utilization and endurance in well-trained male cyclists.
• To compare the efficacy of different CHO supplementation forms during variable-intensity cycling exercise.
• To investigate the relationship between muscle glycogen levels and time to fatigue.

Main Methods:

• Seven well-trained male cyclists performed continuous cycling at variable intensities (45-75% VO2 max).
• Subjects received placebo (P), liquid CHO (L), or solid CHO (S) supplements.
• Muscle biopsies were analyzed for glycogen content; time to fatigue was recorded at 80% VO2 max.

Main Results:

• Liquid CHO supplementation maintained significantly higher muscle glycogen levels compared to placebo after 190 minutes.
• Both liquid and solid CHO supplementation significantly increased time to fatigue compared to placebo.
• Muscle glycogen concentration after 190 minutes was positively correlated with time to fatigue.

Conclusions:

• Carbohydrate supplementation can enhance prolonged, variable-intensity exercise performance.
• CHO intake reduces the reliance on muscle glycogen as a primary fuel source during endurance exercise.
• Both liquid and solid forms of CHO are effective in improving endurance capacity.