They came by bus, train, plane and limo. They came from Novosibirsk and Chelyabinsk, from St. Petersburg and Kazan; they came from places like Kustanai and Oryol, from Vologda and Nizhny Tagil. This small army of 140 hard-bodied women and a few men converged on Moscow to compete in an international seminar of aerobics instructors at Moscow's Olympic Sports Complex.


From 9 A.M to 2 P.M. on a weekend ealier this month, non-stop, in a crowded gym, the women and men stepped and slid, danced and clapped, and huffed and puffed until the sweat poured.


It had taken Tatyana Orlova, 41, from Kustanai, Kazakhstan, a two-day train ride to travel 1,360 kilometers to Moscow -- at a cost of about 150,000 rubles ($45) round-trip.


"It was all worth it," said Orlova, who used to work as a tourist guide some 10 years ago and now teaches aerobics in the industrial Kazakh city.


Orlova's devotion is typical of those who have taken to aerobics, which began in the Soviet Union in 1984 based on Jane Fonda videos and was called rhythmic gymnastics. A few years later the Russians invented shaping, their own version of American aerobics. The difference between the two is that shaping is more geared to stretching and toning, while aerobics focuses on exercising the heart.


In 1991 there was a new boom in American-style aerobics, and the former Soviet Union now has both national and international federations in the sport. Natalia Korkh, national coordinator of Step Reebok and one of the people in charge of the recent seminar, said Moscow has about 200 aerobics instructors, each teaching about 100 people.


After the grueling two-day marathon, first prize was awarded to Julia Chuprikova, 20, of Moscow, who teaches at the National School for Aerobics. She received a $200 gift certificate from Reebok, which sponsored the seminar.


"I will spend it on a pair of sneakers for my aerobic exercises," said the happy winner. "What's left will probably be spent on a Reebok bag."


At the seminar, contestants were judged on the basis of appearance, physical condition, technique, body, charm and presentation. As she looked on, Korh gave a profile of the typical aerobics teacher in Russia.


"The majority of girls were involved in sports, in one form or another, prior to becoming an aerobics instructor," said Korkh, 32, the mother of two. "Like me, most girls were gymnasts. Twelve years ago, after I gave birth to my first child, I needed some form of exercise to get back into shape.


"First, I took up shaping," Korkh said, "but after a while it wasn't much fun anymore. I used to work in front of a monitor all the time. ... In aerobics, you have the instructor on stage, in front of the group. You work with a real person who can create, improvise, make new routines. It is so much fun compared to just lifting your legs and stretching your arms."


Natalia Panina, 28, from Moscow, was a world-class speed-skater in her prime. For almost a year now she has been teaching aerobics. "It is definitely more fun than just doing laps around the ice track," Panina said, grinning.


The oldest contestant was semi-finalist Tatyana Shutenko -- 44 and 1/2, as she put it. "You can stay fit as long as you want to, even when you reach 60 or 70," said Shutenko, who has headed the aerobics club "Educated Body" in Oryol for two years. "At my age, I'm just starting to get better. I haven't even reached my peak."


One of the few men in the room was Viktor Knevets, of Kiev, who ultimately came away with the second prize of a $150 gift certificate from Reebok. Vlada Kutyemova of Nizhny Tagil placed third, winning a $100 gift certificate.


Knevets said he likes teaching aerobics, which attracts mostly women.


"Women can relate better to male instructors," said Knevets, 22, a former Ukrainian national champion in sport aerobics. Asked if he takes a ribbing from fellow males for specializing in a feminine sport, Knevets said, "Most of them don't understand it anyway, and those who do probably envy my position with so many good-looking women around."