A study from the University of Colorado Anschutz, published in the journal Blood Red Cells & Iron, examined the blood of 23 athletes.
Participants ran either 25 miles, equivalent to approximately 40 kilometers, or 106 miles, equivalent to approximately 169 kilometers.
Researchers collected blood samples before and after the races to observe what happens in the body under extreme strain.
They analyzed proteins, fats, and other substances in the blood, as well as red blood cells.
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The role of red blood cells
Red blood cells have a vital function. They transport oxygen and nutrients throughout the body and must be able to bend and change shape to pass through small blood vessels.
After both races, the blood cells were less flexible. There were also signs that they were being broken down more quickly than normal.
The changes were most pronounced in those who ran the longest distance.
According to the study, alterations in blood pressure, as well as inflammation and oxidative stress, may be possible explanations.
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Still unanswered questions
Researchers do not yet know how long the effects last. It is also unclear whether there may be long-term consequences.
The study is based on 23 participants, and further research is therefore needed. No recommendations are given regarding whether to participate in ultramarathons.
However, the findings show that very long-distance runs affect not only muscles and endurance but also the body’s most common cells.
Sources: HealthDay, and Blood Red Cells & Iron.
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