I've read several pieces of research with similar conclusion:

Why working up a sweat enhances our mental capacity is that the hippocampus, a part of the brain critical for learning and memory, is highly active during exercise. When the neurons in this structure rev up, research shows that our cognitive function improves.

Exercise also makes people more resilient to stress:

http://pandawhale.com/post/22868/exercise-helps-your-brain-become-more-resilient-to-stress

It's more important to get exercise and get sleep than to work the extra hours.

So why is it so hard for Americans to adopt this lifestyle?

I don't think so. Americans spend way more time watching television than using computers.

Unfortunately, we have some cultural habits that are antithetical to living healthily - physically, emotionally, spiritually and mentally. I don't think there is one simple answer, but definitely our priorities tend to easily be out of whack. Why else do we live in arguably the most prosperous country in the world, but our levels of happiness, relational connection, and health (just look at the obesity rates) are so disparately low? It's a conundrum wrapped in an enigma.

Perhaps prosperity is correlated with lower happiness, health, and connections?

By the way, I just found this New York Times article connecting exercise and better brain-ing:

http://pandawhale.com/post/12431/exercise-and-the-ever-smarter-human-brain-nytimescom

That is a really complex (and deep) question. It's interesting that only 1 in 3 Americans consider themselves "very happy" in the most recent Harris poll. Maybe our perspective is a bit off and we are a bit too entitled?

http://www.huffingtonpost.com/2013/06/01/happiness-index-only-1-in_n_3354524.html

Remember this article in The Atlantic that made a huge splash a few years ago - "How To Land Your Kid In Therapy"?

“Happiness as a byproduct of living your life is a great thing,” Barry Schwartz, a professor of social theory at Swarthmore College, told me. “But happiness as a goal is a recipe for disaster.” It’s precisely this goal, though, that many modern parents focus on obsessively—only to see it backfire. Observing this phenomenon, my colleagues and I began to wonder: Could it be that by protecting our kids from unhappiness as children, we’re depriving them of happiness as adults?

http://www.theatlantic.com/magazine/archive/2011/07/how-to-land-your-kid-in-therapy/308555/?single_page=true

There is no way TO happiness. Happiness IS the way. ~Thich Nhat Hanh

I am a total believer in that concept. When our goal is our own happiness, we wind up unhappy. When our goal is to live a meaningful, connected, compassionate life, we wind up happy.

...which makes it particularly odd that "pursuit of happiness" is in the American parlance.

Happiness is not something people can pursue.

If a person is pursuing happiness, it's likely s/he is doing it wrong.

But it's unclear that it would have been better for Jefferson to use "the pursuit of property" instead... if you consider the health of civil society holistically. Perhaps the individual happiness quotient needs to be lower in order for the civilization *as a whole* to function better.

In recent years we've certainly seen an increase in the haves versus the have-nots and it's hard to feel like you're "doing it right" when all the trappings of "modern success" (at least as portrayed on contest shows which seem to suggest that success must be achieved through gladiatorial conquest) elude you.

Jefferson couldn't just leave it at life and liberty? He had to add pursuit?

I guess "pursuit of a purpose, meaning and compassion" wasn't as catchy?

You owe your independence to iambic pentameter.

http://www.cinnathepoet.com/blog/2010/04/you-owe-your-independence-to-iambic-pentameter.html

Geege, very interesting! I had no idea the Declaration of Independence had such a parallel to the Elizabethan Sonnet. O joy.

We believe in the interconnectedness of all things.