You don't have to be a marathon runner. You don't have to rough it at night. You don't have to dangle from the side of a mountain — not unless you want to, anyway.

But you definitely can get a workout while you're seeing the world. Active travel — trips that incorporate physical activity such as hiking, biking, kayaking, walking, spelunking, rafting, climbing, horseback riding, etc., or some combination thereof — is an increasingly popular way to put more vigor in a vacation.

Interest in getting out of the tour bus and onto the hiking path is growing so quickly that the travel industry is scrambling to meet the demand.

"This is going to be one of our biggest years, actually," said Scott Schambelan of California-based Backroads (www.backroads.com), which specializes in active travel. "We've had a lot of phone calls, booking up for summer, fall, even inquiring as to winter. … It's on track to be our best year ever, and we've been in business for 34 years."

The boomer generation — more fitness-minded than their elders and some with more disposable income — is helping drive the trend. Jordan Harvey of Minneapolis-based Knowmad Adventures (www.knowmadadventures.com), which offers active tours in South America, estimates that about 80 percent of his clients are people over 50.

"That generation views being healthy as a lifestyle," Harvey said. "They want to go have fun. More and more of them love to be outside and do active things."

Harvey's father-in-law, Greg Kellenberger of Orono, 59, visited Peru last year with his wife and three adult daughters. The trip included a lot of horseback riding and walking among ruins at high elevations.

"We've always kind of done active family kinds of things together," Kellenberger said. "We ski, we canoe in the Boundary Waters. So that was just kind of an extension of how we do trips."

Different expeditions offer different ranges of physical intensity, many well within the reach of anybody in reasonably sound physical condition. Some tours let participants individualize their effort by offering both longer and shorter routes, or making some outings optional. On a bike trip, a staffer might shadow the group in a van, ready to swoop in and fix a flat or offer a lift should anyone decide they'd rather skip that last hill.

"You don't have to be an athlete, you don't have to be in top condition, you don't have to go jogging three miles a day," said Peter Grubb, president of Idaho-based ROW Adventures (www.rowadventures.com). "We have, I would say, something to cater to just about any sort of physical activity that people want."

The flexibility makes active travel ideal for multigenerational vacations, he said. On rafting trips, for example, older folks can choose a bigger, more stable raft steered by a guide, while their higher-energy (or less risk-averse) juniors tackle the white water. "You're all going through the same rapids and can see each other at all times, so at the end of the day, there's this very connected sense of having been together," Grubb said. "And later, grandma and grandpa can be sitting on the beach enjoying a cocktail and some hors d'oeuvres while the kids are playing volleyball and running around in the water."

Which brings up another point. Active need not mean rustic. If, at the end of a rigorous day, you're ready to relax over a glass of wine and a delicious dinner, soothe sore muscles with a massage or hot bath and recharge in a soft bed, many active travel plans provide boutique hotels, spa treatments and other comfy accommodations.

"It's kind of neat, I think, to contrast that rustic adventure thing but being pampered a little bit, too," Kellenberger said. "As I talk to my baby boomer friends, we're all kind of leaning in that direction. We might go out fishing or hiking, then come in at the end of the day and have wine and a really good meal."

Even camping trips need not be rugged or uncomfortable. On ROW wilderness trips, "one way we cater to the over-50 crowd" is by having guides forge ahead and set up camp before the travelers arrive, Grubb said. "So it's camping, but it's very cushy, and we do all the work in terms of setting the tents up and the tables and chairs. There's a kitchen and shower. We do all the cooking and wash all the dishes."

Still, options also exist for those seeking more challenging or outdoorsy adventures. Ward Luthi, of the Colorado-based Walking the World (www.walkingtheworld.com), believes Americans tend to set their own limits too low. The trips he plans can involve hikes of 10 miles or more, climbs of several thousand feet of elevation. Participants aren't in danger, he said, but they learn that "we all can do so much more than we ever thought possible."

Luthi is proud of one particular hike his company offers that features a daunting stretch of terrain. Though often leery of it, participants are encouraged (though not required) to undertake it. Those who achieve it find that "their total mental outlook on what they can do and what life now holds for them is totally different," he said. "When they cross that, all of a sudden their mind accepts, 'Yeah, I can do that.' Some of these same people will then go sky diving."

Katy Read • 612-673-4583