(FORTUNE Magazine) – Some of Ronn Bailey's best work is done on the road. Not traveling for business exactly, but rather racing across Africa in a $300,000 custom-built buggy. Now if most of us were to casually ask the boss for ten weeks off to enter a 7,000-mile African race--"We'll even check e-mail on the road!"--the answer would most likely leave us desk bound. But Bailey doesn't have a boss--he is the boss. Aspiring small-business owners are always warned they'll have to work harder than their corporate counterparts. But as all the entrepreneurs on these pages know, there's a catch: They get to set their own hours. They can telecommute. And if they want to take the afternoon off to ride roller coasters, get knocked around a dojo by a Thai boxing master, or fly around like a modern-day Wright brother, there's nobody to say no. Entrepreneurs say such extreme pursuits make them fiercer and more fulfilled. In other words, getting out of the office could be the best thing for you--and for your company.

■Off-Road Racer Ronn Bailey

Some men buy a regular old Corvette when they're looking for a little midlife excitement. At 54, Bailey, a multimillionaire and CEO of a highly successful information- security company, decided to enter the Dakar Rally, the longest, most dangerous off-road race in the world. This wasn't his first adventure on wheels. He's ridden in the Mayan jungle and north of the Arctic Circle, and one of his goals is to ride his motorcycle on every continent. The Dakar Rally seemed a good way to take on Africa, but after doing some research he decided it was too grueling for a motorcycle. "I thought, I'm 54. There's no way in hell I can drive a bike across the desert," he says.

Instead he had a $300,000 car built from scratch in six months. Bailey bought or commissioned each component: the Jimco suspension, the Fortin Racing transmission, the modified 350-horsepower Corvette LS1 engine, the specially designed and fabricated body, even the paint job. Bailey also had a support truck, a three-axle Renault that has 6x6 transmission (i.e., six-wheel drive), custom-built for members of his team.

The 7,000-mile Dakar Rally begins in Western Europe (Barcelona in recent years; Lisbon in 2006), crosses the Sahara, and ends in Dakar, the capital of Senegal. More than 1,400 racers compete with cars, bikes, ATVs, and trucks, subjecting themselves to perils that include sandstorms, civil strife, bandits, and land mines. Only about half the entrants actually finish. In the 2005 race, five people died, two of them professional racers.

Bailey trained for Dakar by driving a smaller, cheaper version of his custom-built buggy in the desert around Las Vegas. He also persuaded some former Navy SEALs who train military Special Forces in off-road driving to train him as well. "They don't usually teach civilians, but I had two people in my office call them every week for 11 months. They finally gave in," he says.

Nine months later he became the first American amateur driver to race a car in the Dakar, and his entry made news around the globe. The 2005 race began on New Year's Day, and Bailey and his co- pilot, veteran off-roader Steve Myers, immediately found themselves in a violent sandstorm that lasted several days. A week later they took a wrong turn, got lost in the Mauritanian desert, ran out of gas, and were stranded for four days. "We had a sack lunch and one day's worth of water," says Bailey. Eventually someone showed up with gas, and the pair got to their checkpoint, but they had missed the start of the next stage and were disqualified. Bailey figured he hadn't come this far to watch the end of the race on TV. He hired a guide, crossed the Sahara, and arrived in Dakar a week later.

Worldwide exposure for Team Vanguard also meant worldwide exposure for Vanguard Integrity Professionals, the Las Vegas company Bailey started in 1986. The firm develops software that protects the critical information of companies and countries alike. Clients include Aflac and Wal-Mart. During the race he carried military-hardened laptops and satellite phones to keep in touch with the office. "Think of it," he says. "In the middle of the Sahara, literally 1,000 miles from anything in all directions, I could run my company." While the Dakar experience cost Bailey ten weeks of work and $1.4 million, he estimates--perhaps liberally--that the race generated $10 million worth of press coverage for Vanguard.

Of course, that's not why he did it. "It's the ultimate adventure," says Bailey, who calls the Dakar "one of the greatest experiences in my life." His goal for the 2006 race (which starts in Lisbon on Dec. 31) is to finish in the top 20. "I know now that Dakar is not a race," he says. "It's a test of a man's character."

■Vintage Plane Flier Addison Pemberton

He may seem grounded, but nothing could be further from the truth. Pemberton, 51, with his brother Jim, 50, runs Spokane-based Scanivalve, a maker of high-tech pressure and temperature gauges that they took over from their parents. Every afternoon at five, however, he heads to the hangar that houses his collection of vintage aircraft. Pemberton has restored 19 such planes--he now owns six--and has logged some 10,000 hours of flight time. His favorite is the 1931 Stearman 4DM Sr. Speedmail biplane shown here, one of only five in the world, which he takes out for half-hour hops most days. "You feel the wind in your face," he says. "It's a trip back in time."

■Martial Artist Bruce Fenton

When Bruce Fenton wants a workout, he's not interested in treadmills and weight machines. He wants to be kicked in the head. Twice a week the founder and president of investment firm Atlantic Financial drives 45 minutes from his Norwell, Mass., office to a Thai boxing gym, suits up in shiny boxing shorts and hand wraps, and climbs into the ring.

The appeal? Coaches who "push you to your absolute human limit." At the end of his two-hour training sessions he can barely move. "It's punishing," he says. "It's the most strenuous workout I've ever experienced. I've trained for marathons, and that's nothing like this."

Fenton, 33, was hired at Morgan Stanley right out of high school, and by 22 he had founded Atlantic Financial, which became one of the first full-service investment firms on the Internet. His company now has 12 advisors on staff, and his average client balance is $350,000. While building the firm, Fenton had little time for exercise, but he took karate and kung fu lessons intermittently. Last year, soft and out of shape from sitting behind a desk all day, he decided to dedicate himself to improving his martial arts skills. Fenton converted the basement of his new house into a Japanese-style dojo, complete with wooden floors, screens, punching bags, kick bags, weights, and cardio equipment. Now his weeks are consumed with practicing karate, kung fu, and his current passion, Thai boxing. Four nights a week he takes sparring classes, and most mornings he does cardio workouts in his gym at home. In September, Fenton spent two weeks at a boxing school on Koh Samui in Thailand where, for six hours a day, he did nothing but box.

It's a big time commitment, but Fenton has strategies to fit everything in around his company responsibilities. He watches financial news shows during his morning cardio sessions, using a hard drive to skip the commercials. And he recently hired a tenth-degree black belt grand master--the highest level of martial arts instructor--to teach him during his lunch hour on Thursdays. "It helps me save time," Fenton says. "A one-hour private lesson with him might be equivalent to six hours of normal instruction."

On top of the physical intensity of the workout, Fenton feels martial arts give him a significant mental boost. "I find a kind of balance during really hard training," he says. "Suddenly I am focused only on the boxing, not the employee agreement or the revenue projections. My survival instinct kicks in, and it's a lot like meditation. I achieve clarity of mind."

■Roller-Coaster Rider Carole Sanderson

Sanderson has been on more than 500 roller coasters, but that's counting only those in the U.S. As president of the American Coaster Enthusiasts (ACE), she also travels abroad, routinely hitting eight or ten amusement parks in a week. Her trips have taken her as far as Gold Reef City, a park in Johannesburg, along with Tivoli Gardens in Copenhagen and LaFeria in Mexico City. ("People get dressed up to attend that one," she says.) Two years ago, while in Scandinavia, Sanderson logged her 700th roller coaster, and after that she stopped counting.

From Monday to Friday, Sanderson, 44, serves as CFO and partner of Cleveland-based Herschman Architects, which designs retail spaces for clients such as Office Max, Dick's Sporting Goods, Z Gallerie, and Ritz Camera. The firm, founded in 1974, now takes in almost $10 million in revenue. Sanderson's responsibilities often require 60-hour workweeks, but as a co-owner, she controls her schedule. Recently she logged three straight 15-hour days to finish a project before a three-day weekend in San Antonio for the Golden Ticket Awards, an industry event sponsored by Amusement Today magazine.

"Roller coasters are a relief after dealing with the challenges of business," she says. "You just ride. It's a high." Each year she takes on 15 to 30 new coasters, budgeting $5,000 annually for her travel expenses. Acknowledging that she turns "everything fun into a job," Sanderson also spends at least 20 hours a week on ACE tasks. Her expertise has landed her on Discovery Channel specials and in the pages of USA Today, often giving informal reviews of new coaster rides. (Her position at ACE gets her onto them before the public.)

The infatuation started young. Sanderson remembers her first rides as a young girl: the Jack Rabbit at Idora Park in Youngstown, Ohio, and the Blue Streak at Conneaut Lake, an hour northeast of Cedar Point. Her parents took her out of school in Youngstown one winter to attend the opening of Walt Disney World.

Sanderson's favorite coaster is the Phoenix at Knoebel's in Elysburg, Pa. Close behind (and close to home) is the 120-mph Top Thrill Dragster at Cedar Point in Sandusky, Ohio. Until recently it was the fastest coaster in the country, but the 128-mph Kingda Ka at Six Flags Great Adventure in Jackson, N.J., broke its record this past summer. Sanderson hasn't been on that one yet but is planning a trip.

She also likes the older rides. There are 116 wooden coasters in the U.S., and she has ridden nearly all of them at least once. As a rule she can do without too many loops (one or two is fine, she says), and she doesn't like insurance-inspired devices such as seat dividers, head restraints, or ratcheting lap bars. "I like smaller parks--the homespun, family-owned places like Kennywood in Pittsburgh."

Sanderson just returned from a two-week trip through Japan that took her and several ACE members to 18 parks. "The roller-coaster organization has taken me to places I never would have gone," she says. Still, there are 1,817 coasters in the world, so she'll always have new places to conquer. "You can't have a bad day in a park," she says.

■Antique Car Collector Justin Aldi and Ronnie Da Motta

"As a kid, you always want a fire truck," says Justin Aldi, who now owns one with Ronnie Da Motta, his best friend and co-founder of First Security Lending, a Burbank, Calif., mortgage bank they launched from Aldi's living room. First Security has 175 employees and $25 million in annual revenue, and it will handle nearly $900 million in loans in 2005. Aldi, 30, and Da Motta, 31, bought the 1954 fire engine three years ago for $10,000--an anniversary series edition that had spent most of its life in Mason, Iowa. It's the highlight of their jointly owned collection of 30 classic cars and trucks, including a 1927 Texaco truck and a 1966 Triumph TR4. Restoring the fire engine cost them another $20,000, thanks to period-perfect accessories such as a Roto Ray light--a warning signal used on certain trucks in the 1940s. "It's hard to find them intact, but after a three-year hunt on eBay, we got one," Aldi says.

This article was adapted from a story that ran in the October issue of FORTUNE Small Business. Additional reporting by Chris Zappone