Entrepreneurs face considerable mental and emotional challenges, making decisions every day that they hope will pay off for years to come. 

So you probably know that exercise helps you perform better under stress; that exercising at moderate intensity for 20 minutes elevates your mood for up to 12 hours; that exercise increases the production of a protein that supports the function, growth, and survival of brain cells; and that exercise is one of the five daily habits a 30-year Harvard study shows can not only increase your lifespan by 12 to 14 years, but also cut your risk of Alzheimer's in half.

But what you might not know is that a new study reveals a definite link between physical fitness and improved cognitive function -- resulting in improved memory, reasoning, sharpness, and judgment. 

All of which sounds great -- especially since you don't need to be a triathlete to experience the benefits of fitness.

First, participants walked (yes, walked) as quickly as they could for two minutes. Researchers measured the distance completed. (The mean distances achieved were 660 feet for men, 640 for women -- roughly speaking for wearable fitness tracker users, a 16-minute mile, or slightly under four miles per hour.) 

Then they had participants take a variety of cognitive tests. 

The results? As the researchers wrote:

It surprised us to see that even in a young population, cognitive performance decreases as fitness levels drop. We knew how this might be important in an elderly population, which does not necessarily have good health, but to see this happening in 30-year-olds is surprising.

This leads us to believe that a basic level of fitness seems to be a preventable risk factor for brain health.

Just as important, when the researchers took MRIs of participants, they found that "higher [personal fitness] is associated with preserved white matter microstructure and better performance in a wide range of cognitive domains."

Or in less science-y terms, fitter people have greater white matter integrity. White matter is made up of bundles of myelinated axons that affect learning and brain functions and coordinate communication between different brain regions.

OK, maybe that wasn't less science-y. Let's try again: Fit people's brains are built a little better -- which helps them remember, reason, and decide better.

White matter integrity improves episodic memory (personal experiences.) White matter integrity improves cognitive flexibility, processing speed, and fluid intelligence.

In short, white matter integrity helps you better draw on what you've learned in the past to make quicker, smarter decisions in the present.

All from being able to walk a little farther in two minutes.

How to Get Started

If you're overweight, start eating healthier. (Here's a simple place to start.)

If you're out of shape, start exercising more. (Eating well and exercising regularly will also check off three items on the Harvard list of five daily habits, since diet and exercise should naturally reduce your percentage of body fat.)

If you're starting from zero, start walking for 20 minutes every day. Walk out for 10 minutes, and then walk back to your starting point. Over time, try to walk farther on the "out" 10 minutes and even on the "back" 10 minutes. (Because if nothing else, progress is always fun.) 

Your initial goal: Men, 660 feet or more. Women, 640 feet or more.

Then consider adding other forms of cardio, and maybe even a little strength training. (Again, progress is always fun.)

Both will improve your results on the two-minute walking test.

Not only will you feel better, both physically and mentally, but you could also improve your memory, reasoning, decision-making, and ability to make connections and draw on past experiences -- especially under stress.

Can't beat that.