MIKE SHEEN worked for the government for 13 years as a Russian translator and analyst with the National Security Agency. All the while what he really wanted to do was open his own gym, but not some plastic version of Hadrian's villa stuffed with weight-reducing machines and gleaming chrome contraptions. He wanted a gym for serious weight lifters: no frills, just heavy iron for guys to strain and sweat over, bombing their bodies and minds to the limits of biological endurance.

So, Mike Sheen did it. He went to work on an unspectacular frame house in College Park with a dusty white hardpan parking lot. Eventually the front half would house his scuba gear business. And in the back would be the Dynamo Bar Bell Club.

Sheen built the weight room himself with help from his family and some lifters, and he named the gym after one of the Soviet Union's outstanding weight clubs. Dynamo is the only gym in the area that caters to serious lifters.

The place has a relaxed feeling, despite the intense activity. The lifters are consumed by their work but not anxious about it. The atmosphere is so easygoing the Sheen thinks nothing of giving members their own keys to the gym.

Dynamo has some outstanding weight men. The best known is Mike Mentzer, a 25-year-old pre-med student at the University of Maryland who last Oct. 2 own the title of Mr. America.

Mentzer is a darkly handsome man with a ready smile.

"All body builders are colorful, extroverted types," unlike Olympic lifters, who are possessed by their achievements, he said. "Olympic lifting is dull; it can go on for eight hours with the lifters doing exactly the same lifts over and over."

In body building competition, each contestant has a series of compulsory poses and then is allowed to perform others of his own choosing. It gives the sport a freedom not found in competition lifting. The primary goal is aesthetic, not athletic, although a body builder is as much as athlete as any lifter.

"The prejudice against boday builder is probably greater in this country in any other," Menzter said. He blames mismanagement, which has led to an air of sleaziness and carnival freak show at competitions. His own father withdrew his support when Mentzer dropped off his high school football team to devote full-time to body building.

Despite its drawbacks, body building has recently gained in public acceptance. Arnold Schwarzenegger's book and movie, "Pumping Iron," helped. Menzter also credits the women's liberation movement for helping to alter conventional male attitudes about their bodies.

Body builders are judged on muscle size, shape, and definition. General absence of body fat, proportion and symmetry and overrall appearance are other important criteria.

Mentzer uses two sets of exercises. One is to build up his body's mass, or bulk. For this, heavy weights are used with, for example, bench presses for the chest and knee bends for the upper legs.

The second group is used to clarify or increases the definition of the mss of muscle. These call for lighter weights - up to about 150 pounds - that are pumped as fast and furiously as the lifter can stand. This exercise is called razoring, cutting up or ripping, and the combination of the two types of self-inflicted pain and exhaustion is aptly named bombing.

During the period of intense physical exertion, higly oxygenated blood pours into the muscle tissue, causing its pressure. This is called the pump, and body builders swear it's the best feeling in the world.

Mentzer trains just four hours a week, about an hour every other day.

"It's the intensity of the training period, not the length, that's important," he said. "It's a false assumption that more is better . . . there is limit the organism can toletrate; just like getting a suntan - after a certain point the tan becomes a burn.

Although Mentzer's ideas have yet to be fully adopted by other weights men, the notion of intensity as opposed to duration receives greater attention today than just a few years ago.

Body builders can continue in competition well into their 40s and even 50s. Bill Pearl, who was Mentzer's inspiration as a teenager, won the Mr. Universe title at 44. Elliot Gilchrist at 54 is said to be in better shape than when he first began winning titles decades ago. Olympic lifters usually peak in their early 30s, but nobody really knows the peak age for body builders.

Dynamo also has the highest concentration of Olympic lifters in the country. According to Mark Cameron, 24, who came in fifth in the 220-pound class at Montreal, "If a competition were held among Olympic lifters across the country, the men at Dynamo would come in either first or second as a group; only the team from the Los Angeles Y would stand a reasonable chance of beating us."

Olympic lifting has two lifts: the two-hand snatch, where the barbell is pulled off the floor and thrust over head in one single movement, and the two-hand clean and jerk, where the bar is brought from the floor to the shoulders in one motion, stabilized there and then lifted over the head. If you throw up the heaviest iron in either event you win, even if your body looks like Quasimodo's.

The speed with which a lifter gets the weights moving is critical in Olympic lifting, and thus technique, not just brute strength, is often the deciding factor.

Cameron puts in 15 hours of training each week. For him it is not just intensity but also the length of exercise that is important. Cameron wants a world championship and, of course, an Olympic title. He plans to lift competitively at least through the Moscow games.

He said that if the United States is to seriously challenge the Soviets in Olympic lifing, it will have to initiate long-range training programs. Soviet programs extend up to four years, while the Americans tend to work for a specific competition or group of competitions without worrying about what comes afterwards.

Cameron doesn't like the Olympic lifters' image as squat, belly-heavy musclemen. He said most Olympic lifters, other than superheavyweights like the Russian champion Alexeev, are more reasonably "normal" looking than body builders. "Olympic lifters don't like power lifters . . . and they don't like body builders . . . I think body building by itself is useless," he said.

Powerlifting is the third weight format that is considered serious business at Dynamo. It is also the newest, having been recognized as an official sport by the AAU in 1965.

It involves three lifts: the bench press, the squat or knee bend and the deadlift. Powerlifting is essentially brute strength, requiring little technical skill.

Unlike Olympic lifting, where the Soviet Union is dominant, the U.S. reigns supreme among powerlifting nations. For some reason all the major powers in the sport are English-speaking: Great Britain, Australia, Canada, and other former British colonies. These countries want powerlifting included as an Olympic event; the Russians do not.

Body buildings, Olympic weight lifting, powerlifting; that's what they do at the Dynamo Bar Bell Club. Training at any is painful and exhilarating; if you are truly committed to such a regimen there's only one place in this area to go, and that's Dynamo.

For details contact Mike Sheen at 474-8959.