We often hear about the benefits of exercise, and how it can even change your brain.

But let’s take a moment to look at the flipside – how does living a sedentary lifestyle impact your brain?

Researchers at Wayne University School of Medicine wanted to find out, so first, they gathered up some rats.

They put half of the rats in cages with running wheels (on which the rats averaged about 3 miles a day) while the other half were kept in a cage with no wheels, and left to a more sedentary existence.

After 3 months of either running or resting, the rats were injected with a dye to color the neurons in the rostral ventrolateral medulla – a portion of the brain that controls breathing and commands the body’s sympathetic nervous system.

And, interestingly, researchers noted differences in the shapes of the neurons in the rostral ventrolateral medulla between the active rats and the sedentary ones.

They found that while the neurons in the brains of the active rats remained the same shape as before the experiment, the neurons of the more sedentary rats had sprouted far more branches, affecting the sympathetic nervous system (flight or fight response) and making them more sensitive to stimuli.

When the sympathetic nervous system is overly responsive, it can result in confusing (and often times too many) messages from the neurons in the rostral ventrolateral medulla. This causes the nervous system to respond erratically and dangerously.

So, not only does remaining inactive not produce the benefits exercise offers, but it appears that it can actually have a negative impact on the brain as well.

Now, while this study was conducted with rats and not humans, other studies do suggest that people have the same brain region and that it functions similarly.

You can read more about this study in The Journal of Comparative Neurology.