Previously, research has shown that exercise after brain injury can help the repair mechanisms. This new study shows that exercise before the onset of damage modifies the brain environment in such a way that the neurons are protected from severe insults. Jean Harry, from the National Institute of Environmental Health Sciences (North Carolina, USA), and colleagues used an experimental model of brain damage, in which mice are exposed to a chemical that destroys the hippocampus, an area of the brain which controls learning and memory. The team observed that mice that were exercised regularly prior to exposure produced interleukin-6 in the brain, which dampened the harmful inflammatory response to this damage, and prevented the loss of function that is usually observed. This research helps to elucidate how exercise could be used to affect the path of many human conditions, such as neurodevelopmental disorders and neurodegenerative diseases. In addition, as a chemical model of neuronal damage was used, it also raises the possibility that exercise could offer protection against the potentially harmful effects of environmental toxins.