I've written before about how high school wrestling helped me develop the resilience and endurance to be a good entrepreneur. But once an entrepreneur has graduated from college, running is the perfect form of exercise. Here are 6 reasons why.

1. It's cheap and easy

Every bootstrap entrepreneur can appreciate something that's cost effective and doesn't make us dependent on someone else's schedule. If you own a pair of running shoes, you can be a runner.

2. It's energizing

Cash may be the fire that keeps an enterprise alive, but the entrepreneur's personal energy is the oxygen. Without a sense of enthusiasm and passion, the founder will fail to inspire confidence in employees, investors, vendors, customers... not to mention the worried spouse. So we need to find ways to continually refuel. Contrary to the perception that exercise saps a person's energy, I find daily exertion increases my energy level.

During Honest Tea's first five years, when we (unintentionally) operated as a non-profit, we couldn't use cash as an incentive. Instead, I had to instill the belief that there was a bigger impact and a bigger payoff down the road. I quickly learned that the best way to keep the team fired up was by making sure I had enough of my own spark.

As long as I can get at least five hours of sleep, I always fit a run (or a comparable workout) into my schedule. On the rare occasion that I am unable to exercise, I've found that the sleep is fitful because I'm not as tired. Sometimes I find myself running just to make sure that I get a good night's sleep

3. It relieves stress

Entrepreneurs face pressure from all directions, and the tension can be overwhelming. Running doesn't make problems disappear, but it can create rare, solitary moments to gain perspective. And, just as important, running creates moments when I can't take immediate action to deal with the challenges I'm facing. (I never run with a phone!)

If I am about to send out an angry email, I make myself wait to push "send" until after I've gone for a run. Once I've cooled down, I'll re-read the draft email, smooth out a few rough edges, and even delete whole paragraphs.

4. It provides moments in nature

Too much of life is spent in windowless, air-conditioned rooms that are disconnected from the natural world. A morning run, even if it's in the dark at 5 a.m., helps guarantee I am breathing unprocessed air and interacting with the plants and animals around me.

Spending an hour in nature also helps instill a sense of humility. When things are going well, it's not hard for an entrepreneur to gain an inflated sense of power. But an hour outside helps remind us that we have much less control over the world than we imagine -- whether it's spotting predawn planets, a grazing deer, a frozen forest, or the budding green of spring.

5. It teaches endurance and perseverance

In addition to the obvious reminder that scaling an enterprise is a marathon, not a sprint, distance training helps develop the physical stamina required to handle the long hours and travel demands of an entrepreneur.

It also helps reinforce that there is no shortcut to success -- long distance speed doesn't come without consistent preparation, focus, and discipline. An entrepreneur may occasionally get lucky by being in the right place at the right time, but there's no amount of luck that is going to enable a runner to win a distance race without the proper training.

6. It gets your competitive juices flowing

I no longer have the 31:24 10K speed I had in college, but it's still invigorating, and a little intimidating, to step up to a starting line a few times a year. Every entrepreneur has a competitive streak, and while in business we may need to diplomatically suppress our desire to crush our opponents, it's fun to occasionally be blatantly competitive.

Though it can be fun to compete in my age group at a road race, it can also be energizing to run against myself -- an occasional run with a GPS watch, or on a track, helps me gauge my pace and fitness level.

Of course, running isn't for everyone. Some people don't have the ability, the knees, or the fitness levels to run every day, and over the past few years I've taken to biking and swimming a few times a week to give my running muscles a rest. If you're not going to run, I challenge you to consider: what is your substitute activity (or combination of activities) to attain the same benefits that running offers?