As if acting and singing at the same time wasn't hard enough on terra firma, Jill Blackwood does it all while whizzing around a stage on a pair of snow-white rollerskates.

So far, she hasn't hit the turf in tangled mass of limbs as the lead actress in "Xanadu," Theatre's sendup of the 1980 big-budget film flop starring Gene Kelly and Olivia Newton-John. But a couple of spins around the floor of the Kleberg Stage on a pair of wobbly, pink-wheeled skates convinced me that the cast members of the mystical, musical mash-up of Greek mythology and disco nightclubs deserve every penny of the hazard pay they earn for performing on wheels.

Just ask Roberto Araujo, who portrays a muse in the disco-infused show. He's sporting a mean-looking splint on his left arm, the aftermath of a spill he took while trying out some new choreography.

"I stepped on the wrong edge of my skate," Araujo said. He dislocated and fractured an elbow just two weeks before opening night. "I was comfortable on skates. I just let my guard down."

That served as a good reminder to the others to stay vigilant — and upright.

Staging a show in which the lead actress wears skates nearly the entire performance, and others roll instead of walk for various portions of it, presents inherent challenges, according to director and choreographer Nick Demos. That from someone who once directed figure skaters on artificial ice for a Christmas show in Atlantic City.

Demos skated alongside the cast — who practiced in knee pads, elbow guards and wrist pads — during rehearsal, and led drills to help them perfect their skating skills.

Blackwood, who plays the Newton-John character in the show, wanted more insurance, so she invested in a few one-on-one skating lessons with an instructor known as Mr. Rollerskate at Playland Skating Center in Northwest Austin.

"It's one thing to go around a rink and another to skate in a small space and have to do a scene and sing full out," said Blackwood, who skated a few times as a teen.

Everyone learned that skating takes a surprising amount of core strength, even if you're a physically fit actor or actress who regularly practices yoga or dance.

They were sore.

Really sore.

Blackwood dropped a skate on top of her foot, causing a nice bruise. Jennifer Young, who plays a muse in the show, strapped on a heart rate monitor and found out she burned 680 calories in one rehearsal.

Happily, the Kleberg Stage at the Zach is not elevated, so there's no danger of soaring over the edge. It's been coated with a pebbly surface to increase traction, too.

"Nick has us doing fun tricks," Young said. Some cast members spin, others do show girl-esque kicks while balanced on one skate. "Some have been successful and some have not."

"Going backward is the biggest challenge," said Matthew Redden, who plays the lead role of Sonny Malone.

Other minefields to navigate? Negotiating steps backstage — in the dark, while wearing skates. Costume changes. And that fear of careening into the knees of an unsuspecting audience member.

"That's why we don't say ‘break a leg' with this production," Demos said.

Contact Pam LeBlanc at pleblanc@statesman.com or 445-3994. Twitter: @fitcityleblanc