TIME WAS you could impress your friends by letting it drop that you jogged a mile or two through the neighborhood after work in your sweatsuit and snakers.

Nowadays when the talk turns to running, you barely hold up your end unless you do at least five miles a day and are conversant with the fine points of muscle stretching, carbohydrate loading and the Morton's Foot Syndrome.

To get beginners out of the sweatsuit and sneakers stage as quickly as possible, the D.C. Road Runners have been staging a series of three seminars covering just about everything you could plssibly want to know about the sport.

The first session, held last month at the Capital Institute of Technology in Kensington, attracted an overflow crowd. Anticipating 80, the Road Runners had to cope with a crowd of 250, including entire cross-country teams and their coaches. Other were turned away at the door. For the second and third sessions, the organizers arranged for larger quarters at the University of Maryland.

The seminars are the brainchild of David Gottlieb, a 35-year-old marathoner, poet and civil rights specialist for the General Services Administration who gained some notoriety last spring when he was beaten up by two young youghs while out on a training run near his home in Silver Spring. While recovering from the physical and psychic wounds of that incident - he was unable to run more than a mile or two daily for months - Gottlieb found an outlet in introducing others to his sport.

"When I started, I had so many questions, yet there was no one available to answer them," Gottlieb recalled. "People think that if you run a lot you must know a lot, but that's not always true.

"For the seminars, I decided to call on my running freinds; I asked each of them to research and report on a subject area. For the tricky stuff, I went outside my circle of friends to the experts I know: Jack Mahurin, who teaches exercise physiology at Springfield College; my podiatrist, Dr. Myles Schneider; and my 'medicine man,' Dr. Gabe Mirkin. none of the speakers was paid for his services, although the Road Runners did pay Jack's transportation from Massachusetts."

The seminars aim to be exhaustive in exploring all facets of the running experience. There was visible shock in the audience at the opening session when two women runners discussed in detail the problems of running during menstration and finding the right brassieres.

For the second seminar on March 13, Gottlieb cleared the program for one speaker, Mirkin, a Silver Spring allergist, dermatologist and authority on sports medicine, especially the prevention of running injuries. A lean, intense man in his early 40s, Mirkin has described himself as the second-worst runner on the 1957 Harvard cross-country squad (Love Story authory Erich Segal was the worst.)

Mirkin launched his talk by promising that everyone in the room could run a marathon in 18 months by following his advice. he outlined a weekly regimen of three hard workouts and four "job days."

"How do you know when you're working hard?" someone replied.

If recovery from a hard workout takes longer than 48 hours, it was too hard, he sakd: If less than 48 hours, it was too easy.

"Listen to your body; that's the first rule of running," Mirkin declared, adding that most of the running injuries he encounters are caused by people who "don't know what an easy day is."

"The pattern should be stress/recover, stress/recover," Mirkin said, "but they think it's stress/stress/stress/destroy!"

Mirkin asid he learned his lesson through hard experience: "You're looking at a man who trained so hard he broke three bones in his foot. I used to compete with my training diary, trying to run more miles than the week before. After I'd built up to a 100-mile week, I'd have a zero-mile week because of injury. Now there are lots of days if I'm not feeling right, I run 50 feet and then go home."

During a 10-minute break several in the audience came up to the stage, took off their shoes, and showed Mirkin foot and knee ailments. One woman learned she had Morton's Foot, a common structural defect in which the second toe is longer than the big toe. Others compalined of sore Achilles tendons and chondromalachia patella ("runner's knee").

Then Mirkin fielded questions from the floor.

Q. "I've heard it's a good idea to run backwards now and then to use different muscles in your legs. What do you think?"

A. "I think that's an excellent idea if you plan on racing backwards."

Q. "How do you know when you're about to get a knee injury?"

A. "When it starts to hurt."

Q. "My wife tells me I spent too much time with my stretching exercises."

A. "Just what are you depriving her of by stretching?"

Q. "Can I be a marathoner and still play baseball?"

A. "Sure."

Others asked about arthritic knees, drinking beer (all right, but not during competitions), and special exercise drinks (Mirkin thinks they're a wast of money).

The final running seminar will be Sunday at 7 p.m. in the foreign language laboratory next to McKeldin Library at the University of Maryland. Topics include clothes, the runner's environment, endurance, sleep and rest, competition, running clubs, recovery from layoffs, children's running, weight training, commuting on foot, lunch running and "the mental trip."

The D.C. Road Runners are taping the sessions for publication in Running times magazine.