Marathon runners experience a decrease in myelin: study

It’s well known that the bodies of marathon runners and other endurance athletes use fat as an energy source once the glycogen in muscles is depleted. A new study suggests that bodies may not only use body fat to sustain energy during prolonged exercise, but also fat contained in myelin. Myelin is primarily made of lipids, and previous animal studies suggest that in extreme metabolic conditions the body may use the lipids as an energy reserve. Researchers in Spain performed MRI on 10 marathoners before, 48 hours after, two weeks after (two runners) and two months (six runners) after a marathon. They analysed the myelin water fraction, an imaging biomarker of myelin that measures pools of water molecules trapped within myelin lamellae.Read: No pain, no gain? Hardly. This year’s fitness buzzword is ‘recovery’The MRIs revealed decreases in the myelin water fraction after a marathon. The majority of myelin was unaffected but there was a significant reduction in 12 areas of white matter in the brain. The areas are associated with motor coordination and integration of sensory and emotional stimuli.Two weeks after the run, the myelin water fraction values were not fully back to baseline levels. Two months after, the myelin water fraction values had fully recovered.The researchers tested to see if dehydration, either of the entire body or the region studied, would affect the myelin water fraction values but found that brain volumes did not change following the marathon, indicating to the researchers that dehydration could be ruled out as causing the change in myelin water fraction values.The findings indicate another area of plasticity in the brain. “This reversible reduction in MWF upon prolonged exercise and recovery after lowering physical activity strongly suggests changes in myelin structure and content that may open up a new view of myelin as an energy store ready to use when common brain nutrients are in short supply,” the researchers write. “We define this process as metabolic myelin plasticity.”Future studies could investigate if neurological or cognitive functions were affected in the regions where myelin decreased after a marathon. The researchers note that regular, moderate-intensity physical intensity is important for brain health in people of all ages.The paper was published in Nature Metabolism.Read: Inside baseball

Marathon runners experience a decrease in myelin: study

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