In view of the positive effects of voluntary running on the brain of mouse models of various human neurodevelopmental disorders [26,56,57,58], which are accompanied by an increase in BDNF levels, we sought to determine whether exercise, confined to voluntary daily running sustained over a month, could improve brain development and behavioral defects in Cdkl5 KO mice. This evidence concerns the gene CDKL5 and neurodevelopmental disorder.