There are a lot of reasons you want to keep your brain in good working order, not the least of which is that it helps your career. When your brain is working at optimum capacity, you're more creative, efficient, and productive at work. 

But there's another reason to build up that gray matter: to help you stay happy. Numerous studies show that healthy neurological functioning is linked to a more stable mood and the ability to be resilient in the face of stress.

If you're looking to be mindful about your smarts and happiness, there's something you should do regularly that you may not yet be prioritizing.

According to Erica Seigneur of the Stanford Neurosciences Institute, "[T]here is one activity that has been shown to improve working and long-term memory, improves mood, staves off dementia in old age, and in general, makes your brain and body happy."

What is this magic sauce?

Cardiovascular exercise.

That's right: "Exercise triggers a molecular cascade in the brain that ultimately results in an increase in synaptic plasticity," says Seigneur. "This, in turn, is believed to improve learning, memory, and other forms of cognition."

Getting your heart rate up isn't just good for maintaining a healthy brain, either--it actually contributes to brain growth. "Exercise also results in an increase in the birth of new neurons in a part of the brain important for learning and memory called the hippocampus," says Seigneur. In fact, she asserts that cardiovascular exercise actually results in a volume increase in the hippocampus of about 2 percent. 

Neuroscientists aren't the only ones advocating for exercise. James Blumenthal, PhD, a clinical psychologist at Duke University, says, "There's good epidemiological data to suggest that active people are less depressed than inactive people. And people who were active and stopped tend to be more depressed than those who maintain or initiate an exercise program."

In other words, according to broad, population-based correlation studies, when you exercise, you feel better. More hopeful. You're more motivated to accomplish the things in your life you really want to. Plus, according to another paper titled simply Exercise for Mental Health, "Exercise has also been found to alleviate symptoms such as low self-esteem and social withdrawal."

It's easy to believe that in order to improve your brain functioning, you should read complex books or do endless crossword puzzles. And it's easy to think that when you're feeling down, Netflix and a box of Oreos will make you feel better.

While those things may help (temporarily), it's also scientifically proven that an efficient way to help out your brain -- and mood -- is a whole lot simpler:

Go do some sprints.