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Does Distance Matter? Metabolic and Muscular Challenges of a Non-Stop Ultramarathon with Sub-Analysis Depending on
Lucas John1, Moritz Munk1, Roman Bizjak1
1Department of Internal Medicine, Division of Sports and Rehabilitation Medicine, University Hospital Ulm, 89075 Ulm, Germany.
Nutrients
|December 11, 2025
Summary
Ultramarathon running causes significant metabolic and structural disturbances, impacting energy balance and muscle integrity. Personalized nutrition and recovery strategies are essential for ultra runners to manage these extreme physiological challenges.
Area of Science:
- Sports Science
- Exercise Physiology
- Endocrinology
Background:
- Ultramarathon running presents extreme physiological and metabolic demands.
- Limited evidence-based guidance exists for nutrition, energy balance, and recovery in ultra endurance athletes.
- Understanding metabolic and hormonal responses is key to enhancing athlete health and performance.
Purpose of the Study:
- To investigate the metabolic and hormonal responses to ultramarathon running.
- To assess energy balance, body composition, and biomarker changes in ultra runners.
- To correlate physiological markers with self-reported symptoms post-race.
Main Methods:
- Prospective observational study of 43 ultra runners across 100 km, 160.9 km, and 230 km races.
- Pre- and post-race assessments included body composition, energy balance, and biomarkers (leptin, ghrelin, insulin, glucagon, irisin, CKM, LDH).
- Continuous glucose monitoring (CGM) and symptom questionnaires (GASE) were utilized.
Main Results:
- 39 of 43 participants completed the race, with a mean energy deficit of 6797 kcal, primarily fueled by carbohydrates (79%).
- Significant changes in biomarkers indicated disrupted energy homeostasis and muscle damage (decreased leptin/insulin, increased ghrelin/glucagon/CKM/LDH).
- The 230 km group exhibited the most pronounced changes, with increased gastrointestinal and musculoskeletal symptoms post-race.
Conclusions:
- Ultramarathon running leads to substantial metabolic and structural disturbances, irrespective of distance.
- Individualized nutritional and recovery strategies are crucial for ultra runners.
- Further research is needed on the interaction between energy deficit, macronutrient intake, and recovery.
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