Greetings from the Appalachian Trail, Vermont branch. I'm somewhere on a mountainside, hiking through mud. I have a skinned knee and two bruised toes, and did I mention the power-shower rain? So why am I so exhilarated as I follow Sam Benoit, our fearless leader, onto the rock field that leads to the peak? It's the intoxicating pine scent, the heart-pounding view, but mostly the lighthearted feeling I have after two days at New Life Hiking Spa in Killington. It's summer camp for grown-ups.

I've signed on for four budget-friendly days of dawn-to-dusk activities, communal dining, and heavy-duty exercise with an emphasis on the great outdoors. New Life may have the word spa in its name, but it has a lot more in common with Camp Wohelo in Maine, where my 11-year-old daughter goes in summer.

That's fine with me. I'm here for an outdoor mini vacation with a side of R & R—relaxation and reduction. For US$249 a day (plus tax), I get a room, meals (daily total: 1,600 calories), great guided hikes, fitness classes, and a massage. I can reduce my stress level, fat intake, and, with luck, waistline, without major reductions in my bank account.

Any doubts that New Life qualifies as camp are dispelled the first night at dinner, when a delicious tilapia with red beans and vegetables is served. "I can't stay awake after nine at this place," declares a sophisticated Manhattan woman who comes here for a week every summer. As a congenital night owl, I figure I'm immune and chuckle as I stroll back to my room at 10:30. New Life is headquartered in the Inn of the Six Mountains, a rambling, rustic ski chalet open year-round, and signs posted upstairs warn that Quiet Time commences at 10 p.m. I'll say: The hall is stone silent.

I'm up the next day for the 7:30 stretch class, given in a spacious tented exercise room behind the inn. The stretches feel great, but the entire camp appears to be here, and it's crowded. A final deep breath and we beeline for the dining room, where breakfast—a choice of three weight-conscious entrées—awaits us at six round tables, each seating eight. I'm famished but not hungry enough to polish off the greasy scrambled eggs, paired with half an English muffin. "Try the Cheerios," says a stylish Dallas woman, here for two weeks to lose weight, pointing to a dispenser on the counter.

The hiking menu is more appealing than the breakfast one: three itineraries, ranging from a nature walk to a challenging climb. By nine we're piling into vans for the ride to the trailheads. It's my first day, so I opt for Advanced Intermediate and quickly understand why it's so popular: Besides a two-and-a-half-hour climb up Mount Tom, a scenic peak in über-charming Woodstock, we're given an hour to explore the town—and its shops. It's a sunny summer day, and the hike is terrific. At the summit we behold storybook New England: Rolling hills! Clapboard buildings! Steeples! Cows! We follow a different trail down that takes us across a covered bridge to the Woodstock town green and bag lunches.