Long after the crowds have left their office buildings downtown and even the strip joints and porno shops nearby have quieted down, D.C. fireman Jim Martin is still at it, grappling with his 100-pound dummy.

Between fires and other emergency calls, Martin returns to his training room in the basement of the Engine 16 firehouse at 1018 13th St. NW, lifts weights and then grabs, swings and slams that canvas dummy, complete with lifelike arms and legs, all over the room.

This is not a bizarre form of emotional therapy for Martin, 28, a five-year veteran of the fire department who usually works the 3:30 p.m. to 6 a.m. shift.

A compact 177-pounder, Martin is training for his next match, in Caracas, Venezuela, as the United States' entry in his weight class in the little-known amateur sport of sombo wrestling..

Sombo wrestling, a variation of judo invented in the Soviet Union after the Russian revolution of 1917, was made possible by the cultural mixing of Russian people from eastern and western parts of the nation.

Combining elements of free-style wrestling, as practiced in Europe and the United States, and judo, which developed in medieval Japan, sombo wrestling is part of the basic training taught to every Soviet soldier, Martin said.

Although he is not given to he-man talk, Martin is hardly shy when he steps on the wrestling mat.

"In the judo community, I have a reputation as a brawler," Martin said. "I just wear them down to the point where they don't want to put up a fight anymore." He said his goal is to make every opponent leave the mat mumbling, "I hope I never have to fight him again."

Much of the action in sombo wrestling, as in judo, involves the contestant's grabbing his opponent by the standard heavy cotton fighting shirt and trying to "throw" him.

A sombo wrestler can win either by pinning an opponent on the mat for 20 seconds or forcing his surrender by dislocating his elbow, a common occurrence in the sport, Martin said.

Using the device, euphemistically called an "arm submission," a sombo wrestler "straightens out the arm to 180 degrees and attempts to take it past that point," Martin said. "The elbow is a good hinge, but it only goes 180 degrees."

As a result of repeated arm submissions, Martin cannot fully extend his left arm, he said. "But I've done it more than I've received it," Martin said. "You can always hear the cartilege tearing."

The last time he performed an arm submision was in June, when he beat a U.S. Army sombo wrestler from Georgia and qualified for the Pan American Games, to be held later this month in Caracas.

He recalled the moment, in the middle of the fast-moving match.: "I said to myself mentally, 'There's one arm here, and there's one plane taking off for Venezuela.' I thought to myself, 'Sorry, bud.' "

Martin, who took up judo during his high school days in Groton, Conn., said he began sombo wrestling in 1980 when he was training for a judo match. He entered the national sombo championship, held that year at the Bullis School in Potomac and, to his surprise, won a gold medal.

In international matches such as the Pan American Games, the Soviet Union dominates sombo wrestling, Martin said. Yugoslavia, Romania and the United States usually scramble for the silver and bronze medals.

Martin lives with his wife in an Alexandria apartment filled with trophies from international matches.

His sombo wrestling and his firefighting "blend perfectly," Martin said.

"When I walk onto the mat, I see it as a matter of life and death. Then when I'm tired, and I'm trying to decide if it's worth it, there's really no choice but to go on. And in actual life-and-death situations, in a fire, I think of it as a competition, as a challenge, so it allows me to stay calm, and do the job I have to do."