This is your brain on a marathon
- academicmemories
- Sep 4
- 8 min read
Magdalene Dochnal
Over the course of 26.2 miles, a marathon runner’s whole body is pushed to its limits. While much attention is given to the physical strain imposed on an athlete during the event, marathon runners also undergo a mental ordeal. Their brains are tasked with coordinating their movements to maintain healthy form that can sustain 26.2 miles of running, many runners are often trying to be conscientious of particular pacing and fueling strategies for optimal performance, and every athlete is having to keep their focus away from health and performance anxiety and direct it toward achieving their goals on race day.
Just as a marathon runner’s legs require a great deal of energy, so too does their brain. However, exercise science research has long held a gap between insights on neuromuscular physiology and brain physiology as they each relate to endurance sport performance. That is until Ramos-Cabrer and colleagues (2025) introduced the concept of metabolic myelin plasticity and opened the door for fellow researchers to explore how running 26.2 miles changes the brain. Their work not only provides a lesson on how glial cells contribute to brain function, but also on how the brain adapts to the demands of physical exercise.
Introduction to myelin
Myelin is a substance made of fatty acids that encases the axons of many neurons throughout the central and peripheral nervous system. Its main functions are to insulate axons to prevent the leaking of energy from an action potential and to increase the speed at which an electrical signal travels down the axon (Augustine et al., 2024). Myelin is synthesized by different kinds of glial cells, nervous system support cells, based on location with oligodendrocytes myelinating central nervous system (CNS) neurons and and Schwann cells being responsible for myelinating peripheral nervous system neurons (Augustine et al., 2024). Myelin’s function as an insulator is of particular importance in the brain’s control of motor movements as the spinal cord axons that send nerve impulses to the muscles are relatively longer than those which do not leave the brain, meaning there is greater potential for energy to leak from the action potential and a greater impetus for speed to execute movements quickly (Augustine et al., 2024).
Energy use in a marathon: Myelin as energy stores?
An endurance athlete’s primary source of fuel is glycogen, which is broken down for the creation of adenosine triphosphate (Burke & Hawley, 2018). In the brain, that glycogen is stored in astrocytes, another kind of glial cell (Matsui et al., 2017). However, the glycogen stores in these astrocytes are not nearly at the same scale as stores throughout the rest of the body, making them potentially unreliable for endurance sport performance at the level of a marathon (Asadollahi et al., 2024). This presents a problem as the prolonged motor coordination necessary for running a marathon can be significantly taxing on the brain as evidenced by the phenomenon of central fatigue where the CNS struggles to initiate muscle movement (McKenna & Hargreaves, 2008; Tornero-Aguilera et al., 2022).
From this developed the theory that another source of energy may play a more significant role in the brain during endurance sport than it does elsewhere in the body: lipids. While lipid metabolism is often regarded as not being as advantageous a source of energy as carbohydrate metabolism, lipids are still a quality energy source (Burke & Hawley, 2018). Thankfully, the brain happens to be full of lipids via the presence of myelin.
Initial research in animal models had shown that oligodendrocytes are more resilient in low energy availability, glucose-deprived states relative to glycogen-storing astrocytes, suggesting their lipids may be an advantageous fuel source in an endurance setting (Asadollahi et al., 2024). The big breakthrough came when Ramos-Cabrer and colleagues (2025) transitioned this research to human subjects, examining myelin content in brain areas associated with motor control and coordination in marathon runners in the weeks and months after a race. They found demyelination in brain areas with significant connections to the basal ganglia, thalamus, and spinal cord, implicating not only motor control functions but also sensory-emotional integration (Ramos-Cabrer et al., 2025). Perhaps most interestingly, they also found that runners tested 2 months post-race showed myelin content in these areas within normal ranges, suggesting that the brain recovers much like the rest of the body after racing a marathon (Ramos-Cabrer et al., 2025).
Significance for cognitive function
While the novelty of Ramos-Cabrer and colleagues’ findings means that little to no research has been done on how metabolic myelin plasticity on the scale experienced by marathon runners affects cognition, some speculation and inferences can be made from past exercise science and neuroplasticity research.
Firstly, marathon runners should be emphasizing nervous system recovery alongside musculoskeletal recovery following a race. The need for nervous system recovery has been common knowledge among top marathon coaches and runners, but more casual runners may overlook this aspect of recovery in favor of their sore calves, quads, and glutes. While more research is needed to more accurately describe the timeline of myelin recovery post-race and design more effective recovery plans, initial findings suggest the remyelination process may take as long as 2 months (Ramos-Cabrer et al., 2025), a period of time longer than typical coach-recommended recovery timelines (Paul, 2024).
Secondly, the myelin plasticity observed in Ramos-Cabrer and colleagues’ marathon runners may be part of a broader system by which aerobic fitness buffers against aging in the brain. Marathon runners, like other endurance athletes, have rather high aerobic fitness, and this correlates with less age-related brain cell death in older adults (Gomez-Pinilla & Hillman, 2013). This relationship is likely the result of effects on the age-related loss of brain-derived neurotrophic factor (BDNF), a molecule that is broadly important in the maintenance of healthy brain cells and a necessity for neural and glial plasticity (Fletcher et al., 2018). The concentration of BDNF in the brain typically declines as people enter late adulthood, but older adults who engage in aerobic exercise often see increases in BDNF levels (Erickson et al., 2010; Gholami et al., 2025). One explanation for this may be that myelin plasticity as observed in marathon runners requires BDNF to occur, and thus in a “use it or lose it” sense, staves off some age-related BDNF loss.
Lastly, what about those who go beyond 26.2 miles; what about the ultra-marathon runners? Running an ultra-marathon can be uniquely taxing on the brain compared to the 26.2 mile distance. In events like the Hardrock 100 Mile Endurance Race in Silverton, Colorado, runners routinely have to compete for more than 24 hours at altitude above 10,000 feet, barely sleeping along the way (Berger et al., 2024; Bianchi et al., 2022; Knechtle & Nikolaidis, 2018). As such, it is not uncommon for ultra-marathon runners to experience visual hallucinations and reductions in brain volume while competing (Freund et al., 2012; Huang et al., 2021). It is possible that the metabolic myelin plasticity observed in marathon runners may be involved in these phenomena as some of the more affected brain areas are the cerebellar peduncles, nerve fibers which when disrupted may contribute to visual hallucinations (Manford, 1998; Ramos-Cabrer et al., 2025; Winton-Brown et al., 2016). However, this appears unlikely as visual hallucinations originating from the cerebellum are typically associated with disruptions related to cerebellar tumor development (Manford, 1998). Instead, the visual hallucinations of ultra-marathon runners are likely more the fault of inadequate sleeping, fueling, and hydration.
Conclusion
In the hours and days following a marathon, you would be hard pressed to find a runner complaining of soreness in their brain, but the event is as much an ordeal for the CNS as it is for the cardiovascular and musculoskeletal systems. The work of Ramos-Cabrer and colleagues provides an exciting opportunity to combine the fields of exercise physiology and cognitive neuroscience to come to a more complete understanding of how the brain copes with endurance sport. Future research is likely to pair myelin content testing with cognitive and neurological assessments post-race to develop a clearer picture of how metabolic myelin plasticity affects athlete cognition.
Suggested listening
Roche, D., & Roche, M. (Hosts). (2025, April 1). How running may impact the brain, plus Q+A
on body image, heat suits, sweat testing, and nose breathing! (No. 252) [Audio podcast
episode]. In Some Work, All Play.
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