Jane Fonda workouts

In case the 1.2 million fitness fanatics who bought her book, the 3 million-plus who purchased her record, and the 210,000 who exercise to her videotape should need clothes, Jane Fonda is ready.

She's brought out an extensive new line of action fashions manufactured by Capri Beachwear. The clothes, which were previewed here in a Broadway-style production, are in Saks Fifth Avenue and Macy's stores across the country.

The collection isn't, need we say, for the lethargic. Professional dancers who showed the colorful jerseys and sweats at the Shubert Theatre didn't let up for a split second. Many were from the cast of ''A Chorus Line,'' which is playing at the Shubert, and they were giving their fashion-modeling gig their balletic best.

The separates pieces, emblazoned with the ''Jane Fonda Workouts'' label, are as stretchy a line of snap-front leotards and racing-back rib knits as any pumping-iron enthusiast might desire.

As the choreography for the show made clear, the well-tuned body does more than push-ups and jogging. So Miss Fonda's assortment, conceived by her in collaboration with Oscar- and Tony-winning theatrical designer Theoni V. Aldredge (whose credits include costumes for ''A Chorus Line'' and ''Dreamgirls''), takes care of recreational sports, too.

Dancer-models in unitards and leg warmers did jazz and classical ballet sequences, then changed for some footwork in tap shorts. They followed up with gear for the smart gymnast, the well-dressed softball player, and the tireless disco-boogier.

Prices start at $4 for a belt. Running shorts are $22, leotards from $18 to $ 28, a cocoon-shaped baseball jacket $36. A reversible jersey dress of two colors costs $80. The idea behind the clothes is that they can go out of the exercise room into the street. You'd have to have a shower first, though. Nobody did that on the stage at the Shubert.