Got an adventure trip on the calendar? Maybe you're kayaking the Sea of Cortez, hiking Machu Picchu or climbing Mount Rainier. Granted, you might already be in shape, but taking an adventure trip is akin to doing a marathon: You've got to fine tune your body for the demands of that particular excursion. But how?

You've got a few options. You could wing it, of course, and keep up your regular fitness program (you do have one, right?). You could hire a personal trainer. Or you could a customized fitness plan from Fit for Trips.

Fit for Trips was created by an adventure traveler and personal trainer, Marcus Shapiro, to help people get fit for adventure travels. Shapiro and his team of expert trainers (and they do have great qualifications, by the way) partner with adventure tour operators to create fitness programs for specific itineraries. They also design customized fitness programs for individuals and offer support via e-mail or phone.

Hiking is one of my favorite activities, and whenever I travel, I try to hit a trail. I've done tons of cool hikes around the world -- and some not so cool, including one in Costa Rica that landed me in a cow pasture complete with manure. Here are four of that top my list:

1. Kilauea Iki Trail, Big Island, Hawaii

No trip to the Big Island is complete without a visit to Hawai'i Volcanoes National Park, where you could stand within feet of flowing lava. Once there, drive to the Kilauea Iki trailhead for this four-mile, moderate hike. You'll descend through a lush rain forest until you pop out on the crater floor, which is still steaming. Hike your way across the crater until you spot the trailhead going back into the rain forest, now ascending. By the end, you'll have climbed up and down the equivalent of a 40-story building.

Hot air ballooning isn't exactly a high-energy activity. In fact, you'd probably burn more calories slapping together a peanut butter and jelly sandwich.

Still, though, on a recent trip to Albuquerque, N.M., I couldn't resist hopping in a balloon. After all, every October, the city hosts the Albuquerque International Balloon Fiesta, the world's largest hot air balloon festival. How could I not go for a ride in such a hot air balloon mecca? If nothing else, floating that high in nothing but a straw basket would challenge my mental stamina.

I went up with four other passengers through Rainbow Ryders on a beautiful sunny morning and had a blast. My pilot, Brooke, narrated as we floated over the Rio Grande, dipping so low that we were practically skimming the muddy water. Other times, we floated above neighborhoods -- our maximum height was about 12,000 feet -- where only the barking of dogs shattered the silence. (Don't get me wrong: I love dogs, but I was shocked how loud they were.) The experience was so peaceful and serene (besides the dogs!) that I was disappointed when it ended. Yet I loved the after-flight treat: A glass of champagne.

Multnomah Falls Photo: Karen Asp

I'm in love with Portland, Ore. -- and not just because this ultra-hip, eco-conscious city doesn't have sales tax, which even this non-shopper goes nuts over (hello, lululemon!). Hands down, Portland is one of the best places to take an active vacation. Not only does this area offer dozens of fun adventures, the beauty of the area is also simply stunning. Looking for suggestions on what to do? Check out this four-day itinerary.

Day one: Arrive in Portland, check in at the pet-friendly Hotel Monaco and hop on one of the hotel's complimentary bikes. Then ride the streets, cruising through fun neighborhoods like Pearl District, where you'll find some of my favorite restaurants, including Oba and Andina. Grab grub there at night or ride the fare-less light rail to Old Town Pizza or Kells Irish Restaurant & Pub, two of my other favorites.

Day two: Eat breakfast at the Red Star Tavern & Roast House, next to the hotel, which serves delicious sustainable meals. Then hop in your car and drive the Columbia Gorge Scenic Highway on your way to Hood River. Wear hiking gear, as you'll pass numerous trails on the highway, many of them leading to waterfalls. The most popular? The Multnomah Falls, the country's second-tallest year-round waterfall at 620 feet, which has a restaurant at its base. Hike to the top of the waterfall and then keep going on the trail. Or move on to one of the other dozens of trails along the highway. Once in Hood River, check in at the Columbia Gorge Hotel and watch windsurfers on the river behind the hotel. Hood River is famous for its windsurfing, so if you've ever wanted to take lessons, now's the perfect time. For dinner, head into town to Celilo's for an amazing eating experience. After dinner, take a stroll on Hood River's main street.

A yoga break at the Island Experience. Photo: Courtesy of the Island Experience

Tired of indulging in one too many margaritas and slacking off on exercise during vacation? Then you might love a fitness retreat. Although the length of each retreat will vary, the concept is similar: You'll head to a specific destination where you'll focus on healthy eating and daily exercise. Interested? Check out these five (prices don't include airfare):

If you're seeking an adrenaline rush: the Pinnacle Challenge in Palm Springs, Calif.

This three-day, kick-butt retreat will challenge your inner athlete. Each day, you'll do yoga, hiking, water exercise, weight training and yoga. Meanwhile, you'll indulge in organic cuisine and undergo several fitness tests, as well as educational lectures. The bonus? Two massages. Cost: $1,950 single occupancy or $1,450 double occupancy.

Photo: Bob and Mike Bryan, provided by BEST Tennis

They're the coolest doubles team on the pro tour -- and not just because they've amassed over 50 titles, captured an Olympic medal and won all the Grand Slam doubles titles. Mike and Bob Bryan are also twins (Mike's older by two minutes), which is evident when you see them in action. They've simply got a mojo unlike any other doubles team.

The Bryan brothers have been playing tennis together since they were born, after all. And when they're not jamming on the courts, you'll find them jamming with their band.

Even with everything on their plates (including a chance to defend their 2008 U.S. Open title), they took time to chat with That's Fit about tennis, fitness and music. Read on, and you be the judge of how cool these two are (and if you really like them, head to their website and become a member of the Bryan's Bunch).

That's Fit: I'm sure you've been asked this a zillion times, but what's it like to play tennis with your twin brother?

Bob Bryan: We like playing doubles with each other and have done it since we were boys. We're best friends and like doing things together.

TF: OK, but do you ever get mad or upset with each other?

Ana Ivanovic in training. Photo: adidas

Ana Ivanovic fell for the game of tennis when she was just 5 years old. After watching it on TV, she begged her parents to take her to lessons, and the rest, as they say, is history.

Today, the No. 11 seed at this year's U.S. Open (who's also ranked 11th on the Sony Ericsson WTA Tour) can lay claim to several tour titles, including the 2008 French Open. A tough 2009 season and recent injuries may be responsible for her early exit at this year's Open, but she has been working harder than ever off the court to get back into championship form.

Of course, nothing is ever easy as a professional athlete. Not even, you'll be glad to hear, working out! That's what I learned when I chatted with this former No. 1 world player about her fitness program. Two other interesting facts about Ivanovic: She often does Sudoku in the locker room before a match and is superstitious about not walking on the lines of the tennis court.

That's Fit: What are you currently doing to stay in shape? I've read, for instance, that you do long runs, intense sprints and weight training during the off-season.

Ana Ivanovic: That's right. I work very hard during the off-season. I also work intensely during preparation periods during the season. For example, in April before the start of the clay court season, it's important to work on improving the strength in your legs because on clay you need to have a strong, stable base. So I've been working on strengthening my lower body. I also do cardio to maintain my overall fitness, which I think is very good.

Dinara Safina Photo: Getty Images

You know her as the No. 1 player in the world on the Sony Ericsson WTA Tour. (She's also the top seed at this year's U.S. Open.) But what you may not know about Dinara Safina is that she loves watching "Desperate Housewives," she plays soccer, and she has only played her brother Marat, who's on the men's tour, for practice.

Yet the pressure Safina might face if she were to take on Marat for real pales in comparison to what she's facing at this year's U.S. Open. Although she first reached the No. 1 ranking in April 2009, she has yet to claim her first Grand Slam singles title. Can she do it at Flushing Meadows this year? That's a question everybody's asking.

Meanwhile, I had a brief opportunity to chat with Safina about her fitness program. Find out what this top-ranked player had to say -- and why she loves New York City.

That's Fit: How would you rank your fitness level right now?

Dinara Safina: I'm feeling good. I'm working very hard and think I'm in the best shape I've been in.

Photo: mikebaird, Flickr

If you're beach-bound over Labor Day weekend (lucky you!), pack this beach bootcamp workout with you. Exercising on the beach isn't only fun, it's also a great way to challenge your body.

"Sand provides an uneven and shifting surface which makes working out on it more challenging," says Dru Barrios, wellness coach and owner of Ladera Fitness in Laguna Beach, Calif., who designed the following workout. "Your body has to work harder to balance, and as a result, you burn more calories and give that entire body, especially the core, a great workout." There's also less impact on your joints when you do running and jumping in the sand versus hard surfaces, so you're less prone to injury.

To begin, set up two markers on the beach, spaced about 30 to 40 feet apart. Or use landmarks like lifeguard stands. (Try to stick to the hard sand near the water.) Also, keep a water bottle handy. Do a 5-minute walk or jog on the beach to warm up. Then complete the following circuit up to two times, following the modifications if necessary. When you're done, take a 5-minute stroll to cool down.

Photo: FotoDawg/Flickr

I've never liked beets. I blame my mom who forced me to eat them one horrible night when I was 10. My attitude, though, may have to change, as a new study has found that beetroot juice could boost stamina and increase exercise duration.

In this study, published in the Journal of Applied Physiology, eight men aged 19 to 38 drank 500 milliliters of organic beetroot juice for six consecutive days before undergoing cycling tests. They then repeated those steps, substituting a placebo for the beetroot juice.

So how'd they do? Surprisingly well. They cycled 16 percent longer following beetroot juice consumption versus the placebo. "This is an impressive improvement which would translate into a one to two percent reduction in the time to complete a fixed distance," says Andrew Jones, lead study author and professor of applied physiology at the University of Exeter in the United Kingdom, adding that the juice also reduced blood pressure.