"Time Out," Judith Jamison's bright, peppy new work, had the dancers of the Washington Ballet using muscles they never knew they owned, in their full-throttle performance last night.

The Washington Ballet commissioned the piece from Jamison -- the celebrated former star of Alvin Ailey's American Dance Theatre -- with the help of a substantial grant from Exxon. The work's world-premiere engagement this week is the highlight of the Washington troupe's run at Lisner Auditorium, which began Wednesday evening and ends tonight.

The ways in which Jamison's choreography stretches the dancers technically and stylistically are among the strongest features of "Time Out," along with its bracing energy. There are times, indeed, when the four men and four women of the cast have all they can do to keep abreast of the challenges Jamison gives them. The spirit is more than willing, but the flesh is unused to these kinds of demands -- the body-wracking isolations, the rubberized spines, the lightning switches of direction and momentum. The exertions paid off, however, in a prolonged and tumultuous reception from the crowd.

Jamison has delivered what she promised -- a light and playful romp, with no metaphysical overtones or undertones to cloud the kinesthetic exuberance of the dance. She's drawn her materials freely from the sources she's known best as a dancer -- Aileyesque jazz, Afro-Caribbean idioms, American pop and Lester Horton's extroverted modernism, with an admixture of classical basics (though the women aren't in toe shoes).

The ballet is most compelling where it relies the least on formula and predictable unison formations, especially the first two of the four movements. In the rustically flavored first movement the men are sporting bright red suspenders and the women wag their skirts teasingly. There's a passage where the men sling their arms companionably about their female partners' necks, as if they were old buddies. There's another in which the couples, back to back, roll their derrie res sassily at each other. The second movement is a sculptural duet for Janet Shibata and John Goding in which the two seem pulled to each other by invisible drawstrings, no matter how much stage space separates them.

The third movement, with its suggestions of undersea robotics, and the fourth, a sort of whizzing, disco free-for-all, look more standardized in imagery and structure. Ken Hatfield's commissioned score, which uses acoustic and electric guitars, synthesizer and percussion, is effectively functional in its medley of styles, but not otherwise memorable. The costume designs by Sarita Allen and Dean South are attractive and aptly suited to their choreographic mission. Danna Cronin, among the women dancers, and Nat Orr (who's danced with the Ailey troupe) among the men, are the ones who have best mastered "Time Out's" hefty requirements thus far. The others -- Shibata, Goding, Lynn Cote, Lael Evans, Daniel Chait and Barry Baytos -- will improve with more performances under their belts. This is a kind of dancing that needs a lot of breaking in, especially for a classically oriented troupe.

Lack of seasoning was a problem, too, in the company premiere of the balcony duet from Choo-San Goh's "Romeo and Juliet," created two years ago for the Boston Ballet (which, incidentally, is reviving the full-length production in a few weeks). Andrea Dickerson, who was the Juliet, is an appealing dancer of much promise whose looks suit the part, but right now she isn't nearly the actress she needs to be for this kind of assignment. Michael Bjerknes' Romeo also fell short, particularly in bearing and gesture. Goh's choreography has a number of fresh, winning touches, despite its general similarity to other versions, a condition more or less enforced by Prokofiev's gustily swirling music. But it needs the enhancements of a production like Boston's, and dancing of greater dramatic sophistication, to be seen to best advantage.

Balanchine's "Allegro Brillante" was handsomely danced by Cote, Goding and a supporting ensemble of eight, who never let the phrasing become either hectic or mechanical -- common vices in this piece. Still, the dancing never got sufficiently under the skin of the music to make the ballet shine as brightly as it has on other company programs.

It was left to the revival of Goh's "Synonyms" -- a hauntingly imaginative ballet about sexual ambiguities, set to Britten's String Quartet No. 1 -- to achieve the evening's most rewarding union of concept and execution. The splendid cast was headed by Cynthia Anderson and Julie Miles.