When Don Morse, general manager of Piiholo Ranch Zipline, thinks about zip-lining, “;a smile comes to my face and there are butterflies in my stomach! It's as fun and exciting for me now as it was when I first did it.”;

That was 20 years ago, when Morse was a college intern working at an environmental education camp for middle-school children near New Hampshire's White Mountains. It was winter, and a 300-foot zip line was the final element of a snow-covered challenge course that took Morse and his young charges an hour to complete.

The zip line was made of rope on which was tied a sliding metal thimble. Zip-liners held two loops of rope attached to the thimble.

“;I was 19 years old, and I didn't know anything about zip-lining,”; Morse recalled. “;I sat on the edge of the platform and thought, This is crazy! I can't believe I'm doing this!”;

Taking a deep breath, he thrust himself off the platform and felt his stomach drop from the free fall created by the slack in the rope. Once he started to go forward and got his breath back, he loved it.

“;I couldn't wait to do it again!”; Morse said. “;That was the start of the adventure life for me.”;

He went on to build, inspect and run challenge courses for various organizations in Massachusetts, Maine, Rhode Island and Vermont. Zip-lining was his favorite part of those courses, and today he oversees an Upcountry Maui operation that boasts the latest technology for this activity.

Louisville, Ky.-based Experiential Resources, a member of the Association for Challenge Course Technology, built Piiholo Ranch Zipline's course to specifications that exceed minimum requirements. Its zip lines are made of three-quarter-inch galvanized steel cables that can support 58,000 pounds, equivalent to the weight of 10 SUVs. Pulleys connect to the cables at four points to prevent uncontrolled spinning, and a revolutionary braking system ensures smooth, slow stops.

Another great innovation is the nylon harness that participants wear. Instead of the climbing harness used on most other zip-line tours, Experiential Resources adapted theirs from the paragliding harness.

“;They're the only company in the United States that sells this type of harness,”; Morse said. “;It's so comfortable, you feel like you're sitting in a chair when you glide down the lines. Zip-line construction and gear have really improved over the years, but what hasn't changed for me is the adrenaline rush that I get every time I'm standing on the platform, ready to go.”;

  SPREAD OUT over 100 acres and positioned with scenery and safety as top priorities, Piiholo's six lines total almost three miles. They extend over and through thick stands of eucalyptus, wild coffee, koa, ohia, kukui, koaie, guava, strawberry guava and other tropical greenery.

Line Five, measuring 2,800 feet (more than half a mile), is the longest zip line in Hawaii and among the five longest lines in the U.S. It's also the course's highest line, stretching 600 feet above a deep gulch. Fast-trackers will love this exhilarating 40-mph ride and its spectacular views of Central Maui and the summit of Haleakala Volcano.

Anywhere along the course, keen-eyed zip-liners also might spot axis deer, mountain boars, pueo (Hawaiian owls) and Hawaii's endangered state bird, the nene (Hawaiian goose). The ranch maintains a nene breeding habitat.

All tours begin with a walk across a 317-foot suspension bridge. Those who are zipping start with Line One, which is the shortest (480 feet) and lowest (40 feet above a meadow) on the circuit.

“;Four people can zip abreast on that line, which is reassuring,”; Morse said. “;On the rest of the lines, they can zip in pairs.”;

The 42-foot-high Tango Tower, best described as a six-sided jungle gym, ups the course's thrill factor. It features seven climbing structures with names such as Giant's Ladder, Wild Woosey and King's Swing. Accommodating up to 48 people at once, it's an ideal team-building event.

“;When people are in a new situation that's out of their comfort zone or usual routine, they're bound to feel apprehensive,”; Morse said.

“;We see that on the faces of guests who are looking at our Tango Tower and zip lines for the first time.”;

Once they've climbed their first wall or glided down their first zip line, however, they relax and their confidence grows. Said Morse, “;What we usually hear next is, 'That was really fun! Let's do it again!'”;