'School of Rock' Star Alex Brightman Runs 3.5 Miles a Show, Loses a Pound a Day, but Never Stops Going

Matthew Murphy

For Alex Brightman, School
of Rock
is a marathon effort.

The musical, adapted from Richard Linklater’s 2003
film about Dewey, an aspiring rock singer who takes on a substitute teaching
position at a children’s prep school, doesn’t let the Broadway actor stand in
one place as he channels Jack Black’s maniacal energy onstage and introduces
classic rock music to a new generation of kids (both on and offstage).

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“We tracked that on average, I run about 3.5 miles a show,”
Brightman, who earned a Tony nomination for the role, tells ET about wearing a
Fitbit during three shows to calculate just how much he’s running around the
stage. “It’s quite a marathon.”

And the effort is visible, as Brightman sweats (with a
smile) throughout the performance and continues to shed weight -- according to
him, a pound a day -- from his doughy physique. “At some point, I started
looking skinny and fit,” Brightman says of his appearance, which initially was
a choice to personify the character’s laziness. But now, with the producers’
blessing, he’s stopped trying to maintain the weight. “They would rather me be
able to do the show healthier than look bigger, because truly it doesn’t

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What does matter is leaving it all out onstage, especially
for the young performers who can’t seem to contain their energy, even during intermission.

 “I wish they could have a camera backstage. They don't
stop,” Brightman says of his multi-talented co-stars, who perform their own
instruments onstage in addition to acting and dancing in the show. “They’re so
full of energy. At first, I was like, ‘Guys, you have to harness that’ and
trying to mentor them in ways of conserving their energy. But at some point, I
was like, why would you ever stifle that? It’s pure creative energy.”

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With that much energy going into the show, which features a
mini-rock concert at the end of the performance, it’s any wonder Brightman
still is much of a morning person. “It’s the weirdest combination of exhausted
and wired,” he explains. “You’re wired because you just did a show. But with
this one, you just did a show and you also did a rock concert. Your brain is
going, ‘OK, where is the after-party?’”

But now, it doesn’t stop when the musical is over. In April, Stevie Nicks surprised the audience with a lively rendition of “Rhiannon” while backed by the show’s talented performers. And Brightman says it’s only the beginning. “That was the first time we attempted that and quite successfully,” he says. “We have a couple of things lined up.” Though he won’t say who, the surprise after-show performances will fall in line with Nicks, whose music is featured in the musical, and Jack Black, who Brightman says has interest in returning to the show to perform. “It’s just something we want to offer artists: ‘Want to play with some of the best musicians on Earth right now? Surprise, they’re 12,’” he says.

And if nothing else, it’s a treat for Brightman and his older co-stars, who were equally as thrilled as the audience during Nicks’ performance, which included her iconic twirl. “When that happened, I might have thrown up,” he says.

The 2016 Tony Awards hosted by James Corden airs live on CBS on Sunday, June 12 at 8 p.m. ET.