For a great cardio workout, head to the Koko Crater tram tracks.

It's like a giant, outdoor Stairmaster — 1,048 giant steps to the top, to be precise. Besides cardio, the climb up provides an intense workout for the legs, hips, core and derriere.

Fitness instructor Keoni Subiono takes clients up there regularly, mixing in a few other hikes in the area, including the Mariners Ridge and Makapuu Lighthouse trails.

Subiono, owner of Fitness Together in Manoa, challenges his clients to climb to the top once a week as part of his “;12-week transform”; program, in which the goal is not only to lose weight, but to gain lean muscle tone and shape.

Living in Hawaii, we should take advantage of the beautiful outdoor setting, according to Subiono.

“;It adds variety,”; he said. “;It mixes things up and gives you fresh air, plus you can't beat the view from the top. There are few other places in the U.S. where you can work out year-round outside.”;

The fitness benchmark for getting to the top of Koko Crater (elevation: 1,200 feet) is 20 minutes, which his clients aspire to. Every subsequent climb up, the goal is to go faster.

Going up to the top and down can burn an estimated 400 to 800 calories.

Providing an alternative to gyms is important, said Subiono, particularly when the gyms of today have become boxes where people go to hop on a machine and tune everything else out.

“;The gym setting is getting kind of stale,”; he said. “;It's boring.”;

On an elliptical or treadmill, people tend to stare at a television or clock or plug into an iPod to distract themselves from the workout.

The goal at Koko Crater is to improve on speed every time. Besides improvement on cardio, the climb up and down requires coordination. Caution is also necessary because some of the ties of this former tram track are worn. Attention to footwork is required to avoid tripping on rocks and stumps.

“;On the crater you have to focus on what you're doing,”; said Subiono. “;You have to be in the moment and you can enjoy it a lot more.”;

In addition to the climb, Subiono has his clients perform push-ups and sit-ups at the top. Returning back down the tracks, which requires a different set of muscles, is considered the cool-down element of the workout.

“;You don't have to make it to the top the first time,”; said Subiono, “;but it's a trail I like to encourage everyone to work up to.”;

Before a workout at Koko Crater, Subiono suggests eating a breakfast of fruits and nuts, and heading out early in the morning to avoid the hot sun. It's also important to bring enough water to stay hydrated.

Subioni considers Makapuu Lighthouse a beginner trail, Mariners Ridge in Hawaii Kai intermediate and Koko Crater advanced.

Makapuu Lighthouse is a paved, 2-mile contour hike, with scenic views and an opportunity to spot whales (during whale season) en route to the top. There's also an optional detour down to the tide pools via a rock scramble. Mariners Ridge (also known as Kaluanui Ridge) is a 3-mile ridge hike, with a great view of Windward Oahu at the top.

WITH HIS 12-week advanced clients, Subiono mixes weightlifting sessions at the gym with outdoor cardio workouts. Although he offers on-on-one training sessions, his group sessions are popular.

While there can be little social interaction at a gym, take the workout outdoors and it's a different story. Subiono said his clients get the chance to bond through common interests and goals, and often get together on their own to work out, finding they can also get fitness training at a lower fee as a group. They motivate one another and keep one another accountable.

By the end of the program, Subiono's clients typically will have lost anywhere from 12 to 23 pounds.

“;It's a definite challenge,”; said Kasey Jiminez, who had lost 14 pounds by her ninth week. “;I feel like I'm stronger going up every time. We try to take it faster every time.”;

Jessica Reyes, a runner and swimmer, has lost 12 pounds through the program. Compared with a Stairmaster workout, she said the Koko Crater workout is more difficult, involving more core work in order to maintain balance going up and down the mountainous terrain.

And it's more fun, she said.

Ronel Reyes, a Navy employee, lost 23 pounds despite his busy work schedule. He said part of his strategy was to make a lifestyle change, incorporating a better diet and more exercise. He now works out at least four times a week.

Subiono said teaching his clients how to put together a workout on their own and giving them confidence to do so is part of his training approach and philosophy.

He's even worked with clients who have lived near Koko Crater for years but never explored their own back yard.

“;They don't think they can do it,”; he said. His goal is to show them that they can.