Research has shown that regular exercise is good for your gray matter, causing the brain to form new connections, run more efficiently, and even produce new neurons. While hitting the gym gives the brain a boost, a recent study has shown that inactivity can change brain structure, too – in a way that may be bad news for cardiovascular health.
Researchers used rats to simulate gym, well, rats and couch potato lifestyles, letting six rodents run on wheels as much as they wanted (the naturally active rats put in an average of nearly two hours a day) and keeping five others in wheel-less cages, meaning they stayed largely sedentary. After about twelve weeks, the researchers injected the rats' spinal cords with a dye that traveled up to the brain, marking certain neurons. In particular, it marked neurons in the rostral ventral medulla, a small region nestled deep in the brain that helps oversee the sympathetic nervous system, which controls many of the body's constant but unconscious needs, including heart rate, breathing, and blood pressure. Looking at the dyed cells and using a computer program to recreate how the brain region of each mouse looked, the researchers found differences between the neurons of the rats who ran and the rats who didn't.
The neurons of the couch potato rats had more branches, meaning they gathered input from more other neurons, than the neurons of the active rats did. That excess of input in the sedentary rats means, the researchers think, that it's easier to overexcite those neurons–and thus to overstimulate the sedentary rats' sympathetic nervous systems, causing blood pressure to rise and contributing to cardiovascular disease. And sure enough, when they tested the neurons, the researchers could see that their output was enhanced, suggesting they were sending out such heightened signals.
It's likely the same thing that happened in the non-running rats happens in non-exercising humans, the researchers say, and they're hoping to do a follow-up study comparing the brain changes in inactive animals and people. "As humans become more and more sedentary, we think our brains are actually changing in a way that's detrimental," says Patrick Mueller, a physiologist at Wayne State University School of Medicine in Detroit who led the study. "That's part of why you see the increased prevalence of cardiovascular in people that are sedentary."