Day-to-Day Glycemic Variability Using Continuous Glucose Monitors in Endurance Athletes

Area of Science:

• Sports Science
• Endocrinology
• Biomedical Engineering

Background:

• Continuous glucose monitors (CGMs) are valuable tools for measuring interstitial glucose.
• Existing reference values for CGMs are not specific to athletic populations, limiting their application.
• Athlete-specific reference ranges are needed to accurately interpret glycemic variability in sports.

Purpose of the Study:

• To develop athlete-specific reference ranges for glycemic variability.
• To establish benchmarks for interstitial glucose monitoring in elite athletes.
• To standardize diet and exercise conditions for reliable CGM data collection.

Main Methods:

• 12 elite racewalkers participated in two 4-day trials with standardized high-energy, high-carbohydrate diets and daily exercise.
• Interstitial glucose levels were monitored using Freestyle Libre 2 CGMs.
• Glycemic variability was quantified using mean amplitude of glycemic excursions (MAGEs), mean of daily differences (MODD), and standard deviation (SD).

Main Results:

• Twenty-four hour MODD, MAGE, and SD for interstitial glucose were determined to be 12.6 ± 1.8 mg/dL, 36.0 ± 5.4 mg/dL, and 16.2 ± 1.8 mg/dL, respectively.
• Mean 24-hour glucose was higher during the day (102.6 ± 5.4 mg/dL) compared to overnight (91.8 ± 5.4 mg/dL).
• Mean glucose levels were lower in female athletes than in male athletes.

Conclusions:

• This study provides the first reference indices for CGM-derived glycemic variability in endurance athletes under controlled conditions.
• The established reference ranges are comparable to those reported for healthy individuals, despite high training loads and specific diets.
• These findings support the use of CGMs for monitoring glycemic responses in athletic populations.