Sweat, harmonies, and all kinds of awkward dancing flowed freely at Motion City Soundtrack’s RiverFest performance.

Not every band has to stop mid-song during a concert because a large number of audience members have fallen down.

But at the IMU’s April 24 Motion City Soundtrack concert, the group halted its fourth song, “Broken Heart,” and lead singer Justin Pierre had to instruct the audience to “move back, move back, move back” and “be sure to help each other up” before all the people were on their feet again.

That brief snafu didn’t stop students from bouncing back into their frantic hand bobs and torso gyrations, and by the end of Motion City Soundtrack’s one-hour set, both the band members and most of the audience were soaked in sweat.

Putting on this kind of show says a lot about a band and its performance style — it is the rare act that can do so and compel bulky guys in backwards baseball caps to sing along with their eyes closed.

In essence, the concert was not so much a performance but an endurance contest between the audience and the band. Though a clear winner was never decided, Motion City Soundtrack delivered a thoroughly entertaining show.

Unlike other bands, which may not decide to come on until 15 to 20 minutes after a show’s scheduled start time, the quintet broke out “I am wrecked / I am overblown / I am also fed up with the common cold” — the opening lines of “Attractive Today” — immediately at 8 p.m. With the exception of the dancing crisis, the group hardly paused throughout its roughly 20-song set. In fact, the band seemed to gain strength with each successive tune.

Pierre’s voice danced until the show’s finish, and the only indication he gave that his vocals were failing was his request for the audience to sing chunks of Motion City Soundtrack’s last song, “The Future Freaks Me Out.” Guitarist Joshua Cain and bassist Matthew Taylor never faltered in their harmonious backup vocals, and Cain even kicked up his feet like an amateur karate student during “You’ll Always be my Favorite One.” But those moves were no match for keyboardist and Moog synthesizer artist Jesse Johnson, who jammed in a world of his own throughout the night.

Admittedly, an hour of Motion City Soundtrack is a lot of Motion City Soundtrack. Its songs about love and heartbreak are sweet, almost saccharine, and it got to be so much that had I watched a Michael Cera movie afterwards, I might have thrown up. But as the show wore on, the band blew away my misgivings with its almost overwhelming energy and perfect pitches.

Pierre prefaced songs with such introductions as, “This is a song about shit that happened,” and, “This is a brand-new song … just kidding, we actually haven’t written any songs to our new record,” before the group launched into tunes that sounded just as good as the album versions — only much louder.

After the band concluded its set with “Everything is All Right,” the audience called the group back for “one more song,” and wound up with two. The finale was predictable, yes, but nobody was looking for an earth-shattering event. The audience was simply groping for a good time and, judging by the concertgoers’ ebullient, sweat-streaked faces as they walked out of the IMU, they got it.