TORONTO - As she shopped for dresses to wear to this week's "War Horse" opening-night party in Toronto, show puppeteer Dayna Tietzen was struck by the effect the demanding job has had on her muscles.

"I was like, 'My body never used to look like this,"' the Edmonton native, who plays the "hind" of black thoroughbred Topthorn, said in a recent interview.

"I have these coat-hanger muscles now, like, on my neck, and my shoulders are much wider," Tietzen added at the Princess of Wales Theatre, where the all-Canadian production opened to rave reviews on Tuesday.

"I was a dancer, so I used to have sort these long, lean muscles, and (now) my wrists and my forearms when I finish a show are ... not so ladylike. But I'm embracing it."

"I call it the P90 Horse Routine," Ryan Reid, who plays the "heart" of the life-sized beast, quipped in reference to the popular P90X home exercise system.

"We should do a 'Become a Horse' boot camp."

Grant Landry is the other person on their Topthorn team, playing the head of the lifelike equine that was made with cane and mesh by South Africa's Handspring Puppet Company.

Topthorn is the British cavalry pal to Joey, the lead horse who is separated from his beloved farm boy (Alex Furber) and goes on a harrowing journey in the battlefield of the First World War.

Adapted from the Michael Morpurgo novel, the show has already been a smash in London and on Broadway, where it won five Tony Awards. The Toronto version, mounted by Mirvish Productions, marks its Canadian debut.

Tietzen, Reid and Landry have acted and danced onstage, but had never worked with puppets before signing on to "War Horse."

As Topthorn's heart and hind, Reid and Tietzen are inside the horse moving its legs and body and supporting a heavy load (the puppet weighs about 120 pounds, not including the actors who often mount it). Landry is outside the skeleton operating the 20-pound head with his arms and a lever. All three make the animal's sounds.

During rehearsals, the trio focused on building trust and being in tune with one another so they could portray the animal's movements and react to situations without having to talk.

They also went to riding and police stables and did research to learn how horses trot and gallop and react to stimuli.

"We would sort of stand in position -- head-heart-hind, hands on each other's shoulders -- and we would do the scenes that way just ... breathing, learning to make the sounds, moving around the space together," said Tietzen, 26.

"One of our biggest challenges, at least at the beginning, was to learn how to make ourselves disappear," she noted.

Landry, a native of Grande Prairie, Alta., practised using his peripheral vision and noticing things in the room without looking at them.

"When in the horse, let's say if Dayna wants to make a move or go somewhere, Ryan and I can't fight it, we just have to go with it and play with it that way, and how we do that is just by listening to each other," said Landry, 23.

"It's something that was a big part of the training, (to) just be standing there with your eyes closed, listen to the space, react to some sound that someone might make," said Reid, 31, who hails from Victoria.

"Basically the only real job that we have onstage is to be aware, react to it, and I think as far as acting goes, it's the best thing I could've learned from the process."

Their biggest rule when it comes to the puppet is to "treat it like an animal. Don't treat it like a puppet," said Landry.

"It's the respect that we have for the animal and what we're doing. When we're in horse, we are that horse. We're not just, I guess, horsing around, pardon the pun."

Four teams of three puppeteers rotate the job of playing Joey and Topthorn in the Toronto production.

Though they're not the most recognizable faces in the cast -- in fact, the realism they bring to the animals makes it easy to forget they're there -- they take pride in the feedback the horses get.

"Every time they talk about how real the horses were, it's a huge compliment to us," said Tietzen.

"Our moment is at the end when we get our bow, and that's good enough. It's awesome," said Landry.

"It's one of those things where it's a rotating cast, so you don't know if someone's complimenting your team or the other teams, but it doesn't really matter in the end because we are just one big team of horses," added Reid.