The members of German-Swiss theatre group Peng! Palast miss their abs. They lost a lot of fat while taking classes in kickboxing or classic boxing to research the upcoming FIGHT! Palast#membersonly.

The 160-minute performance cum workshop will be staged on Jan 6 and 7 at the Esplanade Theatre Studio.

Performer Nina Mariel Kohler, 32, says: "I was ripped after a few months. I had a lot of muscles and abs. Now we have changed."

She and 30something co-directors Dennis Schwabenland and Christoph Keller are no longer training intensely, but will sweat it out here in the performance inspired by Chuck Palahniuk's 1996 novel, Fight Club.

They will spar in boxing gear, but warn viewers not to expect Hollywood-fast fight scenes.

There will be a sparring workshop and German food cooked by the artists. The work is about promoting social connections rather than simply dealing hurt.

Peng! Palast likes to subvert expectations. In 2013, the group made viewers here confront personal prejudice around the world in the politically incorrect mockumentary, The Holycoaster S(hit) Circus, staged with Israel's Machol Shalem Dance House.

FIGHT! Palast#membersonly is part Palahniuk and part the performers' own experiences working badly paid side jobs until they could make a living doing the art they love.

Schwabenland worked in a gelateria. Kohler used to deliver mail. They understand Palahniuk's bored, insomniac protagonist, who walks through life feeling nothing until illicit fist fights give him a thrill.

Kickboxing and sparring is one way to feel alive and connected to others. Schwabenland, 33, says: "In society, we respect personal borders. Kickboxing together, fists in your face, it's something that crosses your personal border. You get angry or you start laughing."

Kohler says: "It's about people trying to feel something, to put their body in another position. It's a scary thing, but we experienced that it connects you with your feelings and emotions."