If Bob Anderson could erect a bill-board on the fitness road, it would bear just one word -- "Stretch."

"Stretching is the important link between the sedentary life and the active life," claims the 35-year-old "gypsy of stretch." For the past 10 years he has traveled the country, participating in sports-medicine clinics and teaching his skills to professional athletic teams like the Denver Broncos, the New York Jets and the Los Angeles Dodgers.

"It keeps the muscles supple, prepares you for movement, and helps you make the daily transition from inactivity to vigorous activity without undue strain," says Anderson. "It is especially important if you engage in strenous exercise because it helps prevent injuries. And it can be a great tension-reliever if you're sitting eight hours a day and get tight muscles."

Although animals seem to instinctively know how to stretch -- "Watch a dog or cat sometime," sayd Anderson -- "Few people, including professional athletes, know how to stretch correctly.

"Stretching should feel good. The object is to reduce muscular tension and promote freer movement. It is peaceful, relaxing and non-competitive -- a subtle, invigorating feeling that allows you to get in touch with your muscles."

Yet many people pass up this easy "body tune-up" in favor of vigorous bouncing or strenous straining. "In high school," notes Anderson, "coaches say 'take it to the point of pan and then go further.'

"But when you hurt, it's your body telling you something is wrong. You do not have to push limits or attempt to go further each day. Stretching to the point of pain can do more harm than good."

The right way "is a relaxed, sustained stretch with your attention focused on the muscles being stretched," writes Anderson in "Stretching" (Random House/Shelter Publications, 192 pages, $7.95).

Illustrated by his wife, Jean, this bible of the stretching gospel includes routines for stretching specific muscle groups and warm-ups and cool-downs for a variety of sports, from martial arts to squash. "Spontaneous stretches" can be done while watching TV, waiting for a bus or after sitting all day.

A self-admitted "fitness nut," Anderson also throws in some strength-developing exercises, running and cycling techniques, back-care instructions, eating guidelines and a stretching routine for those over 50.

"Everyone can learn to stretch, regardless of age or flexibility," he maintains. "You do not need to be in top physical condition or have specific athletic skills. Whether you sit a desk all day, dig ditches, do housework, or stand in an assembly line, the same techniques of stretching apply."

Not always a lean and muscular 145-pound stretch guru, Anderson recalls "In high school they used to call me 'Squatty Body' or 'Puggy.' I was one of those fat guys (190 pounds, 5-foot-8) with a lot of coordination and pretty athletic."

But as a physical-education major at California State University, he was "low man on the totem pole" in skill-development classes and could not reach much past his knees in a straight-legged sitting position.

He started stretching to relieve this tightness and began cycling and running to get in shape. After watching dozens of professional and college athletic teams stretch, he began developing his own stretching method and started teaching it to others.

"The key is listening to your body. A good stretch isn't determined by how far you go, but by how it feels to you. And each day is different. Some days my body needs two minutes of stretching before running. Other days I need a half hour."

Stretching, he says, can "make you feel more like exercising. It reduces the tensions in the body and promotes circulation to the point where you start to feel springy and bouyant. Instead of being tired, you're ready to go out and do something."

Stretching alone, however, won't provide cardiovascular fitness, and should be part of a physical-fitness program, notes anderson, who runs 90 minutes a day and is an avid cycler.

Perhaps his best reason for stretching is the "use-it-or-lose-it" axiom. When unused, "muscles become weak and tight. We lose touch with our physical nature and life's energies.

"It's a question of feeling good, being healthy and staying alive."