Maybe it's the borscht, maybe it's the vodka, maybe it's something that filters down from the Urals. Whatever the secret ingredient is that revs up these Russians to dance with such explosive velocity, energy and pizazz, they seem to possess it in unlimited quantities.

In all likelihood, the stage of the Kennedy Center Concert Hall is still throbbing to this very minute from the pummeling by feet, knees and hands disched out in the course of the Festival of Russian Dance Friday night.

Perhaps one reason folk dancing from the USSR seems so much more ample and spectacular than from anywhere else is the huge slice of geography and culture involved.

The program for this particular festival assemblage, for example, drew upon the folk ensembles of seven Soviet republics -- Siberia, Moldavia, Byelorussia, the Ukraine, Uzbek, Georgia and Lithuania -- each with its own customs, language, dress, music, lore and characteristic steps and rhythms. The cumulative impact was little short of overwhelming.

Artistic director for the festival was Mikhail Godenko, who heads Siberia's Krasnayarsk Dance Company, one of the participating troupes. From the evidence of the production, Godenko has a keen eye for effect and a sizable flair for staging folk dance in a theatrical but never hokey manner. This wasn't folk dance "in the raw"; the hand of a master impresario was everywhere visible, and though the material of the dances is clearly of peasant origin, the dancers of this company aren't common villagers but highly trained, flamboyantly adept professionals.

No verbal accounting could convey an adequate impage of the range, momentum and virtuosity of the performances, which included silken gliding dances for the women, eyepopping jumps, barrel turns, knee flips and sparking swordplay for the men, and prestissimo stepping, tapping, stomping and kicking by all.

Spectacular as it all was, the program did reach, in both halves, a point of diminishing returns, mainly because of the unremitting pace and dynamism of the selections. After a time, even the most dazzling bravura feats get to be numbing if there's not sufficient relief of tempo and energy level.