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Story summary
- A study published on February 18, 2026, finds ultra-marathon runners suffer red blood cell damage and anemia risk.
- Researchers at the University of Colorado Anschutz link the damage to stress from extreme endurance running.
- Damage appeared in both the 25-mile and 106-mile races, increasing with distance.
- Lead researcher Travis Nemkov from the University of Colorado Anschutz says the long-term health effects remain unclear.
