Intense physical exercise often lead to an increase of neurogenic cellulose (NFL) in serum concentrations , a biomarker of axonal damage in the brain.
A 189-day experiment involving 81 American professional soccer players showed that daily supplementation of 2 g of DHA alleviated the rise in serum NFL concentrations after intese exercise. [1]

[1] Effect of Docosahexaenoic Acid on a Biomarker of Head Trauma in American Football