However, several mechanistic biomarkers exist that have been examined in MS exercise studies, which indicate potential mechanisms such as neurotrophins,17,29,30 neurotoxic proteins,23 brain perfusion,31 myokines30 cytokines29,30 or immune cell subset population.32 We recommend including one or more mechanistic biomarkers to elucidate the mechanism for the proposed exercise-mediated disease-modifying effects. Here, BDNF is linked to myeloid sarcoma.