There are a couple of reasons Sean George is sweating.

One is that, despite it being 37 degrees outside on a Monday night, fans of the band Vostok 4 have pretty well filled the upstairs performance space at The Middle East, maximum occupancy 194. The body heat is approaching stifling.

The other is that George is cavorting like a madman. The other members of the band are in a semicircle at the sides and back of the stage, leaving just enough room for their singer and frontman to dance — leap, jerk, twist, spasm, spin, flail and contort himself — as though to three musical threads at once: the thunderous drumming of Mathew “Cutty” Foster; sinuous, spooky keyboards of Max Butler; and insistent pulse of Tim Correira’s bass guitar.

George is not just sweating. He’s drenched. He’s red-faced and his bangs stick limply to his forehead. When a song ends — cutting off just as the volume and intensity made it feel like the stage was about to explode — George sags, glances at Butler and says to the audience, which is still clapping and hooting, “Every show we play a game: When will the fat man die?”

Indeed, as Vostok 4 brings to a climax its next song, “(Not) Craigslist Killer,” George’s frenzy stops and he collapses to the floor, lying face down and breathing deeply. The band plays on and someone in the audience comes over eventually to poke him and see if he’s okay. George hops up and starts singing again.

(That’s actually only the first of two times George winds up on the floor that night. The second time is with Correira, because the two knock their heads together when Correira started jumping around too.)

Vostok 4 performances display great, coordinated musicianship — three of the band members have been together since they were kids performing blues-rock on Martha’s Vineyard, and Cutty is simply a ridiculously good fit with them  — and prove the band will do pretty much anything to give people a good show, even if it involves premature death (George is 25) or the risk of looking uncool.

“What you’re seeing is true, honest, genuine spaz,” Butler confirms some weeks later at Vostok 4’s South Boston rehearsal space, referring to George’s exertions.

‘The way live shows should be’

“That’s the way live shows should be,” Cutty says. “That’s the thing about this band that I love. It’s a live fucking band that can play. Even when we’re practicing, it’s high energy … I’ve been on the Boston scene at least 10 years, but this is the first band I’ve been in where every show we have, the place is packed and everyone is psyched.

“One of the best compliments we ever got was from an old girlfriend of mine, who’s not a dancer at all,” he said, “and she’s like, ‘This band makes me want to dance.’”

There is a spacey vibe injected into the repertoire via Butler’s keyboards, but it’s not ponderous or slow. Vostok 4 is like an “X-Files” musical written by Joss Whedon specifically to see how fast and loud people can sing, play and dance.

The Vostok 4mula clicked into place neatly. The members of the band like pulp art — you can see examples taped to George’s lectern at shows, postcards of posters for ridiculous movies such as “I Was a Teeny Bopper for the CIA” — and share a nerdy compulsion for songs telling atypical stories. Even as the Road Apples, their band before Vostok 4, George, Butler and Correira were singing a seven-minute prog-rock epic called “Laika,” about the dog shot into space by the Soviets.

The sound evolved “organically,” George says, inspired by Butler’s choice of synthesizer, while choosing a new band name “was a long, annoying” process. The Cathodes, Ronald Ray Gun, Space Bitch … all were debated and rejected, or already taken. The band learned after the Road Apples to check; that there was already a band called the Road Apples is ridiculous enough, but what were the odds the band was from Cambridge?

A quick Wikipedia search produced Vostok 4, and suddenly the band had a sound, a name and a tone: space, sex and communism.

‘We’re not the normal’

“That was a fear of mine at the beginning, that we sounded too weird,” George said. “We’re not the normal, run-of-the-mill thing. But yet, we go play somewhere where there’s people that only listen to the most bland of stuff, and they still manage to like it.”

Correira remembers when Vostok 4 opened for a band that was similar musically but didn’t move much while playing. And were boring. “You have to be entertaining,” he says. “You’re on the freaking stage, you might as well make something happen. If you’re just going to stand there, what’s the point? We hit each other’s heads when we jump around. It’s more fun when you do that.”

The result of butting heads onstage and not off: People at shows stop the men of Vostok 4 to offer congratulations and good reviews. Even sound engineers, members of other bands and fans of other bands. And audiences grow slowly and consistently. While the first show was solidly larded with friends of the band, now it’s friends of friends and people who’ve come to a club to hear other bands but decide to stick around.

Vostok 4 doesn’t expect to be the next big thing. Its members would like to keep doing what they’re doing — and maybe tour New England a bit, maybe someday open for a band at the Middle East Downstairs (it fits 575 people) with a similar energy and retro feel. King Khan, or Freezepop. Definitely get into a studio and record.

For now, it’s enough to do great shows with good crowds — even late on a frigid Monday night, when people have every excuse to stay in and watch a DVD.

“I have no delusions. The kind of music we play, there’s not much you can do to become super big. It would be just be fun to get a band that could have a good-size following,” Correira says.

“And maybe a pair of underpants thrown at us,” George interjects.

“And maybe a pair of underpants thrown at us,” Correira agrees.

Vostok 4’s next chance to spaz out and earn underwear is Sunday at T.T. the Bear’s Place, 10 Brookline Ave., Central Square, Cambridge. Just listen for the synthesizer, make your way through the dancing crowd and look for the dancing madman.