Trail Running (per Wikipedia) - v - Trail running generally takes place on hiking trails, usually single track, but fire roads are not uncommon. The trails are usually inaccessible except at the trail heads. The trails traverse mountains, forests, deserts, and narrow passages.  Steep inclines or rough terrain sometimes may require hiking or scrambling, normally covering thousands of feet of elevation gain.  For this reason there is a particularly ravenous following in the Mountain States, and the Western US.

I personally got hooked in the Gunnison National Forest surrounding Crested Butte, CO.  The ever changing wild flowers that can get chest high make a particularly stunning backdrop to run through.

Many individuals prefer running trails for daily training and exercise, while other trail runners spend weeks out in the backcountry in what is becoming its own sport. A growing number of people are participating in solo backcountry trail running trips otherwise known as wilderness running.  While an ordinary backpacking expedition may last for 5-8 days, averaging 8-15 miles per day with 50lb -60lb backpacks, a wilderness runner will do the same trip in 2-4 days, covering much greater distances each day, and carrying only 20lb packs of minimal equipment. 

And you thought that the Leadville 100 was extreme.

"According to a 2010 special report on trail running published by the Outdoor Industry Foundation, 4.8 million Americans ages 6 and older participated in trail running in 2009." 

Thank you Wikipedia.

While I initially designed the MaxX K for soccer, I tested it trail running, playing tennis, playing soccer, and hiking.  I had never trail run before moving to Crested Butte, and quickly became infatuated and very spoiled. 

I could never road-run again.
(Unless being chased by a bear or elk through town.)

But that is still better than sucking car exhausts and being chased off the road by someone turned around yelling at the kids while on cell phone.

But I digress.  The MaxX K was designed with input from David Manthey, who is not only the director of Runner's Edge of the Rockies, but also puts on the Bear Chase 50 mi Race (with 7,200' of elevation change).

The biggest changes that David suggested were a way to reduce chaffing.  Because while I run 3-5 mi, David regularly runs 50-100mi races.  And at those extreme distances, chaffing becomes a serious issue.