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Fact-checking Furious 7: Can you really break out of a cast by flexing your muscles?

The Rock in Furious 7.
The Rock in Furious 7.
Alex Abad-Santos is a senior correspondent who explains what society obsesses over, from Marvel and movies to fitness and skin care. He came to Vox in 2014. Prior to that, he worked at the Atlantic.

The megahit Furious 7 features cars parachuting into the mountains of Azerbaijan, an ambulance knocking a predator drone out of the sky, and a car flying from one Abu Dhabi skyscraper to the other.

But there's one stunt that rises above the rest, and it doesn't even feature an automobile. It features a man, his cast, and five words.

Hobbs (Dwayne "The Rock" Johnson) sits, frustrated, in his hospital room while carnage fills the streets of Los Angeles. Ruthless mercenary Mose Jakande (Djimon Hounsou) rains down hellfire from a military helicopter onto Hobbs's great city. A predator drone fires missiles at streetcars. And black-ops assassin Deckard Shaw (Jason Statham) is right in the middle of everything. Hobbs, hobbled after a run-in with Shaw and an explosion, is broken. His arm is in a cast, and he's had enough.

Someone needs to protect his city and his friends.

Hobbs flexes his barrel-size arm, breaking his cast. White dust flies. The cast crunches in defeat before splintering. And then Hobbs mutters what might be the best sentence to fully capture the machismo emanating from this film franchise:

"Daddy's gotta go to work."



Like many sequences in this movie, this scene pushes the boundaries of plausibility. Is it possible to break a cast by flexing the muscles of your broken arm?

"It's certainly not impossible," Dr. Eric Novack, an orthopedic surgeon, told me.

Breaking a cast with the muscles on your broken arm would be very painful

As past Fast & Furious movies have taught us, Hobbs is more durable than the average man. That he spends roughly 87 percent of Furious 7 in a hospital room is both an acknowledgment of Deckard Shaw's lethality and the seriousness of Hobbs's defeat.

There is no official diagnosis of Hobbs's injuries, but he flew out of a building, landed on top of an automobile, and braced a woman's fall into said automobile. He spends most of the movie bedridden, and he appears to have broken a bone in his arm. However, the extent of the break and its location are unclear.

That said, breaking a cast with a broken arm would be painful for anyone, including Hobbs.

"I don’t think that any patient can break their cast by flexing their muscles — if it’s a well-applied regular-weight cast, I think the patient would hurt himself first," Dr. James Rickert, an orthopedic surgeon in Indiana, wrote to me over email.

Novack echoed this statement.

"Generally speaking, in the early stages [of an injury], it's going to hurt too much to bend it like that and break the cast," he said. "I would suspect that if your arm was broken, it would probably hurt too much to break the cast."

Thus, the reality of the situation becomes a question of how high you think Hobbs's threshold for pain is. The entire movie plays out over just a handful of days, meaning Hobbs's broken bones and injuries are still fresh. Obviously, Hobbs isn't a regular guy. Like all characters in this film franchise, he's just a little bit superhuman. So he very likely has a higher threshold for pain, making this part entirely possible.

Breaking a cast with your muscles requires a poorly constructed cast and a lot of strength

Both Novack and Rickert explained that the construction of the cast would also be key to being able to break it.

"It does come down to the issue of how much plaster you use and how strong the person is," Novack said.

Novack explained that his younger patients (12- and 13-year-olds) find innovative ways to break their casts over time. This usually involves weakening the cast, sometimes by getting it wet with sweat or water. But he also said he's seen casts break apart from general use.

"Usually it's not quite as dramatic as what's in the movie there," Novack added.

Rickert points out that a thin cast might also make this scene a reality.

"[It] could only work if the cast was applied poorly, or was quite thin — a badly made cast can be weak," he said.

Hobbs's cast doesn't look weak or thin, though. It's pretty thick and burly, made for a thick and burly man. But he's surely stronger than the cast is thick, right?

"There is no question: if someone wasn't hurting, if someone was strong enough, and if the cast wasn't reinforced enough in certain spots, someone could definitely do what The Rock did in that scene," Novack said.

There's one more thing

Perhaps the most unrealistic part of the entire scene has nothing to do with strength at all. It's what the cast is made of. Both Novack and Rickert explained that fiberglass has replaced plaster, as with the kind of cast that Hobbs is sporting. Plaster is mostly used in splints and in specific cases.

"Plaster casts still are used when the fractured bones need to be held in a very certain way so they heal properly — in other words, they can be used when the cast really needs careful molding," Rickert said.

Fiberglass, which is lighter and more water-resistant is the go-to for cast construction, and has been since before Novack began his residency in 1996.

"Fiberglass casts don't tend to fail in exactly the same way [as plaster ones]," Novack said.

Seeing The Rock's arm break through a fiberglass cast might not offer the same satisfaction as The Rock's bulging forearm bursting through thick, chalky plaster. So I asked Novack if he had ever seen anything like what The Rock did to that plaster cast.

"I would be impressed to see it," Novack said, laughing. "But I'm not sure I'd want to be there to witness it."