HEAVENLY BODIES" is the first exercise tape to be expanded into a full- length movie, if you don't count the complete works of John Travolta. It looks like "Footloose" for dinner theater and compares unfavorably with the "Jane Fonda Workout Tape for Expectant Mothers."

Aerobics, the entrepreneurial spirit, single parenthood and balloon bouquets make this a movie for the '80s, however, when a young unwed mother quits the typing pool and makes her dream come true by opening a successful aerobics studio in Toronto. It's called Heavenly Bodies.

Canadian starlet Cynthia Dale, a fresh- faced, strong-winded dancer, debuts as Samantha, executive in tights. Sam's natural vitality quickly attracts the media, a new beau (Richard Rebiere) and the envy of a dancercize instructor (Laura Henry) at the rival Sporting Club. No sweat. Heavenly Bodies decides to settle the score once and for all and challenges the Sporting Club to an aerobic marathon, nine hours of straight leg kicks, pushups, "Maniac" jogging and other forms of physical activity designed to get you winded. A kind of Spa Wars.

Playboy coproduced the film, so a little sexploitation is to be expected, but Dale and her company fare rather well under the circumstances. Dale, given her choice of leotards, opted for more modest cuts, and retained artistic control of her brief nude scene with her lover. Director Lawrence Dane and cowriter Ron Base (a film critic for "The Toronto Star" who'll never live this down) have either intentionally or accidentally come up with a feminist manifesto. Samantha shows an independent streak by refusing to give up her career to follow her man to Chicago.

But "Heavenly Bodies," with its skimpy plot and commonplace choreography, is sure no trend-sweater.

HEAVENLY BODIES (R) -- At area theaters.