My friend John Harkey walks, bikes and practices sustainable living in Nashville, Tennessee.  I loved his essay on walking and thought you might enjoy it too.  You can read more of John's writing at
www.Harkeyresearch.blog.com  
Walking
In
 his essay of the same title Henry David Thoreau repeated the phrase 
wrongly ascribed to Horace Greeley: “go west young man, go west.”  Actually,
 Thoreau was talking about “walking” west, and for him the more precise 
direction was “southwest,” away from his village home (Concord), and 
away from the city (Boston), in the direction of the setting sun.  In his essay, he said he was going to make an “extreme” statement.  As he describes his walks, and the ambition of walking, the word “extreme” seems mild
.
For
 Thoreau a daily four-hour walk was the minimum duration, and more was 
preferred. His walking “ambition” was to leave civilization entirely, 
avoiding the well traveled path and claiming the uncharted wilderness to
 the south and west as his home. His “home” in the village was merely a 
starting place for his walking adventure, but his destination was the 
Pacific Ocean, or maybe the Rocky Mountains.
  
Unfortunately, or maybe to our good fortune, Thoreau never made it that far.  In
 fact, his pace wasn’t very rapid, and he was easily diverted. If you 
have ever been on a spring wildflower walk, you will know what happened.  Every step or two there is something new and unusual for a botanist/poet to look at, and if you are in a group, comment on.  Thoreau,
 like Christopher Robin, knew a lot about the 100-acre wood, but a 
4-hour walk might take him one place in his imagination (say to some of 
the Greek Isles as he followed the meanderings of Odysseus), but while 
thinking about Odysseus he might be observing some ant platoons outside his 
door re-enacting their version of the Trojan war.
For
 me, a walk in the wilderness is a deep pleasure. But my wilderness 
walks are a part time occupation. I take those walks several times a 
year, but in my daily walks (and bike rides), I turn Thoreau’s treatise 
on its head, and turn towards the city, to meet friends, to purchase 
coffee, to shop for groceries, and to enjoy the pleasures of the urban 
experience, which are many.
  
Thoreau, of course, did too.  His sustenance was more from the village and the city than from the wilderness.  He
 thrived on the intellectual stimulation of Concord and the wider Boston
 community, and he enjoyed friendship. He wrote about the horrors of the
 village (“most men lead lives of quiet desperation”), but was really sustained by The Village.
For
 Thoreau, walking was an elite activity. While it involved only a modest
 investment of money (good shoes, sturdy clothing, and a hat), it 
required time.  In Thoreau’s day, the only people with “time” were the wealthy and the occasional bohemian poet.  The
 men (and women) of quiet desperation walked to work and to market, but 
otherwise were busy creating the economic engine that won the Civil War.
 
One
 of Thoreau’s more memorable trips was taken by train rather than on 
foot, from Boston down to New York, and there he met a promising new 
urban poet, Walt Whitman, who had just been “found” and promoted by 
Thoreau’s mentor, a Mr. Emerson.  Thoreau had just 
published his masterpiece, Walden, a year earlier (1854), and Whitman 
had just published his first edition of “Leaves of Grass.”
In
 contrast to Thoreau, Whitman looked toward the city and its thriving 
masses of people for inspiration rather than to the uncharted wilderness
 near Thoreau’s cabin. Whitman’s walk is also open ended —walking “the 
long brown road before me leading wherever I choose”—but is about those 
he meets rather than where he goes—“the felon, the diseased, the 
illiterate person” and “the escaped youth, the rich person’s carriage, 
the fop, the eloping couple.” And, the objects of civilization: “planks 
and posts of wharves, rows of houses, porches” and then the ideas, the 
“philosophies” and the “music.”  Whitman’s walk was an 
exploration of culture—the city—rather than fields and forest, and he 
liked what he saw, as much as Thoreau liked wilderness. 
  
I
 like both walks. For my wilderness walks, though, I take part of the 
city with me, in the form of a friend or two. Climbing up a mountain 
along a shady path, we observe the beauty of a cascading stream while 
discussing whether charter schools really make a difference.
Walking
 is easy, requires no new expenditures, can be fit into a busy 
lifestyle, and helps you maintain health. It’s also fun, or can be. 
Twenty minutes a day (just over a mile) is helpful to health.  Forty minutes (2-3 miles) will help you maintain weight, and with healthier eating, possibly lose weight.  Either distance gives you time to think (alone) or banter (with friends), improving your mood and your friendships.
Thoreau
 set the bar too high, leaving his quietly desperate neighbors behind as
 he walked “away” from the Village. Today, in Nashville at least, the 
Village is the spark, encouraging its residents to leave the desperation
 (the TV, the computer, the couch, the bag of potato chips) behind, and 
take a walk (on the new greenway or sidewalk) “into” the Village.
For a description of one of the more interesting urban walks in America, try this:
http://www.nytimes.com/2013/07/22/nyregion/high-lines-best-kept-secret-its-a-fast-commute.html?hp
Research note on Walking for Health
Two
 researchers at University College of London conducted a meta-analysis 
of 18 observational studies (460,000 participants) on the health effects
 of walking published between 1970 and 2007. Their study was summarized 
in the August 2009 edition of the Harvard Health Letter. 
- Walking reduced 
the risk of dying by 32% during the study period. The study period 
averaged 11.3 years for the studies reviewed. )  
- The risk of cardiovascular events was reduced by 31%.
- Benefits of walking were found for people walking as little as 5.5 miles a week at a pace of 2 miles per hour.  Greater protection was obtained by more miles and a more rapid pace
Here is a link to the Harvard Report
http://www.health.harvard.edu/newsletters/Harvard_Mens_Health_Watch/2009/August/Walking-Your-steps-to-health