Go for a Walk and See the World : Popular tours promote health and some up-close sightseeing.

According to a recent poll conducted by the National Sporting Goods Assn., based in Mt. Prospect, Ill., walking is the most popular exercise in America with more than 65 million participants. The over-50 segment of the population comprises a substantial portion of that total for several reasons: Walking is something almost anyone can do; walkers can choose their own pace, and walking doesn’t require special clothing or equipment.

Organized walking vacations have grown to the point where they are now arranged by more than two dozen companies in the United States. Itineraries include trips to every state in the United States, every province of Canada plus locations in Europe, New Zealand, Nepal and the Caribbean. Some walking tours have a specific purpose, such as the observation of natural history, the viewing of historical sites and landmarks or the exposure to cultural aspects of the areas visited. Others are merely sightseeing excursions planned for the purpose of observing at leisure other lifestyles or parts of the world.

Walking tours vary in duration from a weekend to two weeks. The pace can be as little as three or four miles a day or as many as 10. Rest and refreshment stops are frequent. The size of a walking group is usually limited to 10 to 20 people. Vans accompany walkers and carry luggage and refreshments, and may be used by walkers who wish to ride part of the way. Since most walks are through back-country areas off the beaten track, overnight stays are usually in small towns or villages.

The following are sample itineraries, prices and other information provided by three companies that specialize in walking tours. Prices listed are for the land-only segments of a tour, and do not include air transportation to and from the destination. Prices vary by season, length of tour and location. In most cases, prices include three daily meals, park entry fees, guides, support vehicles, accommodations, taxes and gratuities. Prices are per person, double occupancy.

--British Coastal Trails specializes in walking tours in England, Ireland and Scotland, and offers more than 30 eight-, 10- and 12-day tours of the coastline and countryside of the British Isles. Hiking areas bypass most major cities and encompass untrammeled areas in places such as the Scottish Highlands, Yorkshire lake country, Cotswolds, Cornwall and Devon, and western Ireland. Prices range from $1,395 to $2,295 per person, and include accommodations plus breakfast and dinner daily. For a brochure, write to British Coastal Trails, 1001 B Ave., No. 302, Coronado, Calif. 92118, (619) 437-1211.

--Country Walkers offers one of the largest selections of walking tours, from May through November. Many of the trips are limited to weekends, though others may be for as long as 10 days. Emphasis is on natural history, and hikes range from four to nine miles per day for a duration of three to five hours over easy-to-moderate terrain. Sites include Maine and Vermont, Arizona’s Sonoran Desert, the Olympic Peninsula in Washington, the South Island of New Zealand and southwestern Ireland. Country Walkers employs guides who are naturalists, historians, photographers, teachers and world travelers.

The six-day fall trip in the Sonoran Desert begins at a guest ranch and includes visits to the giant cactus forests of Suguaro National Monument, the San Xavier del Bac mission and the Arizona-Sonoran Desert Museum. It is priced at $1,299 per person. The Pacific Northwest trip is six days in a beautiful backwoods area of Washington, and costs $1,399 per person.

For a brochure, contact Country Walkers, P.O. Box 180, Waterbury, Vt. 05676, (802) 244-1387.

--Walk Europe is offering one- and two-week walks in Switzerland and England and combines itineraries that include small villages, farms, medieval towns and great cities. Walks are scheduled for approximately two hours in the morning, with a stop for lunch, then two to three hours in the afternoon, all at a leisurely pace. Three one-week tours are scheduled for 1992. Trip No. 1, the “Heart of Switzerland,” is described as “easy; hills and level terrain.” It begins in Zurich and ends in Bern. Price is $995 per person. Trip No. 2 is “North and South Switzerland,” with walks on mountain trails and frequent rest stops. Price is $994 per person. Trip No. 3 is in England’s Cotswolds and passes by manor houses, medieval churches, rose-covered cottages in stone villages and English pubs, ending at the home of William Shakespeare in Stratford-on-Avon. The price is $1,094 per person. A folder with information and itineraries is available by contacting Wander Tours Inc., P.O. Box 8607, Somerville, N.J. 08876, (800) 282-1808.