Looking to increase your brain size? You may want to try aerobic exercise, a new study suggests.

Researchers found that participants who exercised aerobically four times a week for six months showed greater increases in brain volume than participants who exercised for that same amount of time by stretching.

"This type of result is always encouraging, especially because the study shows changes not only in brain volume, but also in cognitive function," said Max Wintermark, a professor of radiology at Stanford University, who was not involved with the research. [Aerobic Exercise: Everything You Need to Know]

In the study, researchers looked at 35 adults with mild cognitive impairment (MCI), which is considered an intermediate stage between the normal cognitive decline associated with aging and more serious conditions like dementia. The researchers assigned 16 of the adults (whose average age was 63) to the aerobic exercise condition, and assigned the other 19 (whose average age was 67) to the stretching control group.

The participants also underwent an MRI (magnetic resonance imaging) brain scan at the beginning and end of the six-month study. MRI scans use magnetic fields and radio waves to create detailed pictures of organs like the brain. In addition, the researchers tested the participants to see whether their exercise routine effected their cognitive performance.

It turned out that all of the adults in the study showed some increases in the volume of their brains' gray matter, which is made up of the type of neuron that is responsible for tasks such as processing information and controlling muscles, according to the study.

But the participants in the aerobic exercise group showed greater increases in volume in a few regions, including the corpus callosum, which consists of the nerve fibers joining the left and right hemispheres of the brain, the researchers said in their study. [The 4 Types of Exercise You Need to Be Healthy]

And in fact, the participants in the stretching group showed decreases in volume in an area of the brain called the right posterior corona radiata, which carries information to and from the brain regions that are responsible for thinking and perceiving.

In addition, participants in the aerobic-exercise group showed improvement in their executive function after these six months, while participants in the stretching group did not. Executive function includes skills such as working memory, problem solving and reasoning.

The results suggest that aerobic exercise interventions, more so than exercises such as stretching, could help preserve or even improve brain volumes in people suffering from MCI, the researchers said. This is especially significant considering that people with the condition are at risk of developing Alzheimer's disease, which today affects more than 5 million Americans, the researchers said in a statement about their findings.

Still, Wintermark told Live Science, "this is a relatively small study, and it definitely needs to be confirmed in a larger population."

However, the finding may help shape additional research into brain-related changes of different types of exercise.

Original article on Live Science.