Effect of Low vs. High Carbohydrate Intake after Glycogen-Depleting Workout on Subsequent 1500 m Run Performance in...

Area of Science:

• Exercise Physiology
• Sports Nutrition
• Metabolic Adaptations

Background:

• Carbohydrate (CHO) metabolism is vital for high-intensity, short-duration exercise.
• Limited research exists on glycogen availability's impact on trained athletes in field settings.
• Understanding pre-exercise glycogen status is key for optimizing athletic performance.

Purpose of the Study:

• To investigate the effect of manipulated pre-race glycogen reserves on 1500m time trial (TT) performance.
• To assess physiological responses, including stride pattern, heart rate, blood lactate, glucose, and oxidative stress, under varying glycogen conditions.

Main Methods:

• Eleven trained middle-distance runners (4 female) underwent a glycogen-depleting session.
• Participants consumed either high (>5 g/kg/d) or low (<1.5 g/kg/d) dietary CHO for two days prior to a 1500m TT.
• Measurements included performance time, stride pattern, heart rate, capillary blood lactate, blood glucose, and plasma malondialdehyde (MDA).

Main Results:

• 1500m TT performance was significantly slower by ~2% (4.5s) in the low CHO condition compared to the high CHO condition (p < 0.01).
• Lower baseline and peak blood lactate concentrations were observed in the low CHO condition (p=0.022, p=0.039).
• No significant differences were found in blood glucose or plasma MDA levels between conditions.

Conclusions:

• Restricted pre-exercise carbohydrate intake impairs 1500m time trial performance in trained runners.
• Glycogen depletion reduces baseline and peak blood lactate responses during high-intensity exercise.
• Blood glucose and oxidative stress markers (MDA) are not significantly affected by short-term CHO restriction in this context.