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Glucose dynamics during ultramarathon running: a multi-phase framework and implications for late-stage glucose
Kengo Ishihara1,2, Hiromi Kosaka1, Hirokazu Taniguchi1
1Faculty of Agriculture, Ryukoku University, Shiga, Japan.
Frontiers in Sports and Active Living
|June 15, 2026
Summary
Ultramarathon running shows distinct blood glucose phases, including late-stage increases not explained by diet or intensity. Continuous glucose monitors (CGMs) may aid personalized nutrition strategies for endurance athletes.
Area of Science:
- Exercise Physiology
- Nutritional Science
- Endocrinology
Background:
- Ultramarathon running presents extreme physiological stress, necessitating tailored nutrition for optimal performance.
- Understanding glucose dynamics is crucial for endurance athletes to manage energy levels and prevent fatigue.
- Continuous glucose monitors (CGMs) offer a novel approach to track real-time glucose fluctuations during prolonged exercise.
Purpose of the Study:
- To review glucose dynamics during ultramarathon running using CGM data.
- To propose a conceptual multi-phase framework for understanding these glucose changes.
- To explore potential mechanisms behind observed glucose patterns and their implications for nutrition.
Main Methods:
- Mini-review of existing literature on ultramarathon running and glucose metabolism.
- Analysis of data from continuous glucose monitors (CGMs) in ultramarathon runners.
- Conceptual framework development based on observed glucose patterns across three distinct phases.
Main Results:
- Glucose dynamics during ultramarathons can be divided into three phases: initial elevation, gradual decline, and increased variability with late-stage elevations.
- Late-stage blood glucose increases are not fully explained by carbohydrate intake or exercise intensity alone.
- Potential contributing factors include altered substrate utilization and cumulative inflammatory stress impacting glucose uptake.
Conclusions:
- CGMs can reveal trends in glucose dynamics during ultramarathon running.
- Observed glucose patterns suggest complex physiological responses beyond simple energy intake.
- Further research is needed to elucidate mechanisms and refine individualized nutritional strategies for ultramarathon runners.
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