The joys of hiking, rafting, caving and all manner of outdoor adventures are being discovered by thousands of Americans who are newcomers to the wilderness. Not as likely to have grown up envisioning themselves climbing mountains, piloting kayaks through rapids and the like, these newcomers--women--are discovering the special exhilaration and satisfaction in meeting challenges of the out of doors.

"People need to get out there and have an experience where they stretch their limits, do things they never thought they could do," says Ann Zabaldo, founder and director of Great Encounters. "Especially women."

Zabaldo, 32, a former D.C. consumer-education specialist, started out conducting conventional assertiveness-training classes for women but found them "frustrating."

"Talking about having more confidence," she says, "did little to bring changes in the individuals."

For many women, she acknowledges, summoning the self-reliance to deal with physical challenges is a novel experience. "This is why experiences in the outdoors are such an effective method for improving women's leadership and management skills."

On a typical Great Encounters venture, a group of eight to 10 women grapples with what is called the Ropes and Initiatives course, laid out and conducted by the staff of Inner Quest, Inc., in collaboration with Ann Zabaldo. Widely used by outdoor training groups, R & I is a graduated series of "events" that incorporate physical, psychological and interpersonal challenges. Some activities call on group effort.

In the Electric Fence, for example, the entire group must cross over a string at waist level without jumping or hopping over. Other activities offer individual physical and psychological hurdles. In one, participants cross rope bridges 30 feet off the ground to reach a treetop platform. Hooked to a pulley system, each steps off the platform and rides the cable down at breakneck speed.

In a follow-up session the next day, participants discuss their experiences and relate them to situations in their daily lives.

Commented one woman in her mid-thirties, who mastered each event of the day: "My husband and my two sons like me to do things with them outdoors, but they don't expect me to be able to handle myself very well. I needed to get away and do this with other women to see how capable I actually am."

A 27-year-old secretary told the group: "It's hard for me to take charge of any situation, but now I have a better feeling about my ability to face up to something, even when it scares me to death. I hope I can take that confidence back with me to the office."

In these 1 1/2-day courses and in the more informal Great Encounters activities like bicycling or cross-country ski trips, Zabaldo sees the critical ingredient as participants "going beyond their limits, finding out they can do more than they thought."

The impact of the outdoors on women is seen daily by Sandy Sklar, head of Washington Women Outdoors (WWO), which organizes trips and training programs in hiking, sailing, rock-climbing, cross-country skiing and bicycling (including pre-conditioning and equipment-maintenance).

"Doing things outdoors is a good experience whatever group you're with," says Sklar, 42, a former research psycholgist, "but there is something unique that happens when the group is all women, led by a competent woman instructor. For one thing, there's a feeling of taking complete responsibility for ourselves. When a car won't start at a remote ski area, for example, we have to deal with the situation ourselves."

Sandy Sklar, herself a late-comer to the outdoor life, got "hooked" after spending a summer in Switzerland in 1977 during which she did a lot of hiking in the Alps. When she returned to this country and looked around for others interested in the outdoors, Sklar found that existing groups were short on people like herself: novices of 30 and over, particularly women.

She decided to organize a cross-country ski clinic for 12 participants; more than 600 calls from interested women came in. "Clearly," she says, "there were lots of women around who were eager to get involved in outdoor experiences and attracted to the idea of a supportive atmosphere to develop skills and confidence."

Slowly but steadily, Sklar found herself evolving Washington Women Outdoors to respond to that need. WWO is now an organization of 450 members, with many more women participating in activities.

Both Washington Women Outdoors and Great Encounters are oriented to women confronting outdoor activities together. A large number of coed options for the outdoors also are available. Still, according to many who have given both coed and all-women activities a try, there is a particular pleasure in the women-only experience.

Some women describe feeling more immediately at home when they are taking on tough new challenges in the company of their own sex. This ease is often particularly appealing to those women whose jobs involve high-power competition in a largely male environment.

"We get silly together," says a 35-year-old government-agency director. From a 26-year-old computer programmer: "There's a great sense of camaraderie, knowing we pulled ourselves and each other through."

Others mention the nurturance and supportiveness. As one 40-year-old housewife-turned-entrepreneur sums up the experience, "It's just fun being out there with a group of women--housewives, career women, students--working hard on something and depending on each other."