Marathon runners’ brains actually consume their own protective nerve coating as emergency fuel during races, but remarkably can regenerate this essential tissue within weeks.
At a Glance
- Brain scans reveal marathon runners experience temporary reductions in myelin—the fatty substance insulating nerve cells—after races
- Scientists believe the brain breaks down myelin as an emergency energy source when conventional fuels are depleted during extreme endurance events
- The myelin levels return to normal within two months, suggesting this adaptation causes no long-term harm
- This discovery could provide valuable insights for treating conditions like multiple sclerosis where myelin deteriorates without regenerating
- The research raises questions about potential risks for people genetically predisposed to certain neurological conditions
Your Brain’s Emergency Energy System
When marathon runners push their bodies to extremes, their brains employ a surprising survival tactic. New research reveals that during these intense endurance events, the brain may temporarily break down its own myelin—a fatty insulating substance that coats nerve cells—to use as an emergency energy source. This adaptation occurs in specific brain regions related to motor coordination and sensory processing when other energy reserves become critically low during prolonged physical exertion.
Myelin constitutes approximately 40% of the brain and plays a crucial role in facilitating the transmission of electrical signals between neurons. The study, which examined brain scans of marathon runners before and after races, found noticeable decreases in myelin levels following competition. These changes were most prominent in areas responsible for movement control and integrating sensory and emotional information—precisely the regions most active during long-distance running.
Temporary Changes with No Lasting Damage
While the idea of your brain consuming its own protective tissue might sound alarming, researchers found no evidence of long-term harm. Follow-up scans revealed that myelin levels in the runners’ brains fully recovered within two months after the marathon. This remarkable regenerative ability demonstrates the brain’s extraordinary adaptability to extreme physical challenges and its capacity to restore critical structures when normal conditions resume.
The study involved ten marathon runners who underwent brain imaging both before and after completing races. While researchers documented clear changes in myelin levels, they did not assess whether these temporary reductions affected cognitive functions or physical abilities during the recovery period. This limitation suggests a need for additional research to fully understand the implications of this brain adaptation mechanism.
Implications for Neurological Conditions
The discovery that marathon runners’ brains can recover from temporary myelin loss has generated excitement among researchers studying neurological disorders. In conditions like multiple sclerosis (MS), myelin deteriorates progressively and typically does not regenerate effectively. Understanding how healthy brains naturally restore myelin could potentially open new avenues for developing treatments for demyelinating diseases.
However, the research also raises cautionary questions about potential risks for individuals with genetic predispositions to neurological conditions like amyotrophic lateral sclerosis (ALS). Some scientists suggest that regular extreme endurance training might pose additional risks for these individuals due to repeated myelin degradation, though more comprehensive studies are needed before drawing definitive conclusions.
The Resilient Brain
This research highlights the remarkable resilience of the human brain in adapting to extreme physical challenges. When faced with the extraordinary energy demands of marathon running, the brain prioritizes survival by temporarily sacrificing non-essential components for fuel, then efficiently rebuilds them when resources become available again. This adaptive capacity demonstrates why regular physical activity, even in less extreme forms, can contribute to long-term brain health and cognitive function.
For older adults concerned about maintaining neurological health, these findings underscore the importance of regular physical activity—though not necessarily at marathon intensity. The brain’s demonstrated ability to adapt to physical challenges and repair itself suggests that appropriate exercise might help maintain neural resilience as we age, potentially offering protection against age-related cognitive decline.
