Any place where the terrain is rough and the sky is blue in Dallas, Houston or elsewhere in Texas is a place you'll probably find mountain bikers. The sport of mountain biking usually refers to riding bicycles, which possess particular design characteristics, off-road, although sometimes the term simply refers to riding a mountain bike.

It's a tough, demanding sport that requires endurance, good bike handling skills and a lot of self-reliance. It's an individual sport that can be performed almost anywhere. There are certain aspects of mountain biking that are similar to trail running, more so than regular bicycling. And, because riders are often far from civilization, there is a strong ethic of self-reliance. Seasoned riders have learned to repair their broken bikes or flat tires to avoid being stranded in the middle of nowhere. This reliance on survival skills accounts for the group dynamics of the sport. Club rides and other forms of group rides are common, especially on longer treks.

Mountain biking can be roughly broken down into five categories: cross country, downhill, freeride, dirt jump and trials/street riding. And, even though there are five very different terrains to ride upon, most mountain bikes have a similar look: knobby tires, large round- frame tubing, and some sort of suspension or shock absorbers. Mountain biking can be done anywhere from a backyard to a gravel road, but the majority of mountain bikers prefer to ride trails which they call singletrack -- narrow trails that wind through forests, fields, deserts or mountainsides.

The bicycle has really been no stranger to off-roading since its invention toward the end of 1800's. The modern sport of mountain biking originated in the 1970's with several groups of riders in Texas and other areas of the U.S. making valid claims to playing a part in the sport's birth.

Riders in Crested Butte, Colorado, and Cupertino, California, tinkered with their bikes and adapted them to the rigors of off-road riding. Other riders around the country copied their friends who rode motorcycles off-road, and then began riding their bikes in a similar fashion.

However, a group in Marin County, California -- recognized by the Mountain Bike Hall of Fame -- played a central role in the birth of the sport. They began racing down Mount Tamalpais on old 1930's and '40s Schwinn bicycles, retrofitted with better brakes and fatter tires. This group included Joe Breeze, Otis Guy, Gary Fisher and Keith Bontrager among others. It was Joe Breeze who built the first new, purpose-made mountain bike in 1977.

Tom Ritchey built the first regularly-available mountain bike frame, which was accessorized by Gary Fisher and Charlie Kelly and sold by their company called MountainBikes. The first two mass produced mountain bikes, the Specialized Stumpjumper and Univega Alpina Pro, were sold in 1982.

Mountain bikes differ from road racing bicycles in several ways. They have a smaller and stronger frame, knobby, as well as wider and higher-profile tires, which are mounted on a rim that is stronger and more durable than a standard bicycle rim. They also include a larger range of gears, to facilitate climbing up steep hills and over obstacles; a wider flat or upwardly rising handlebar that allows a more upright riding position; and, often, some form of suspension system for either the front wheel or both wheels.

The inherent comfort and flexibility of the modern mountain bike has led to an estimated 80% market share of bike sales in the United States, United Kingdom, Canada, Australia, New Zealand and other countries. While it is estimated that only between 10 and 20% of mountain bikes are actually ridden off-road, the sport of mountain biking has seen an explosion in popularity and diversification.

There are environmental concerns regarding a number of outdoor extreme sports, but properly-built mountain bike trails have little negative environmental impact. Studies reported in the IMBA (International Mountain Bike Association) Trail Solutions manual have shown that a mountain bike's impact is comparable to that of a hiker, and substantially less than that of an equestrian.

But irresponsible use, such as using a trail when it is too wet, can be damaging, whether the individual is on foot, bike, or horseback. It's clear that other activities, such as horseback riding and ATV or motorcycle use, are far more damaging. Improper routing or trail construction techniques may result in a trail that does not hold up well to any kind of use. Riding in rainy conditions can create ruts and holes in the trail, making it less usable.

Physically demanding sports such as mountain biking can be a great way to exercise to maintain good health.