Anybody who will go to a movie with a title like this one starring a professional wrestler bearing the name of an inanimate object should know perfectly well what to expect, and it’s certainly not any cerebral quality. And “The Scorpion King” surely shows few signs of narrative intelligence–it’s a thoroughly brainless series of pumped-up action sequences, leavened with historical howlers of such absurdity that one almost admires their shamelessness. The fact that its protagonist rides a camel and the accident that much of it is set in a desert are all it shares with a film like “Lawrence of Arabia.” Yet it’s professionally stitched together and moves along reasonably well: if what it is is what you want, you should find it an amusingly trashy retread of the conventions of 1940s serials.

Nominally the flick is a spinoff from 2001’s exhausting special-effects extravaganza “The Mummy Returns,” in which Dwayne Johnson, aka The Rock from his World Wrestling Federation persona, showed up briefly as an ancient warrior exhumed from centuries of sleep–his appearances were mostly in the GGI form of a half-human, half-insect composite. Stephen Sommers, the writer-director of both “Mummy” movies, has–along with William Osborne and David Hayter–concocted a backstory on the fellow, in which Mathayus, as he’s called, is the sole surviving Akkadian (with all due apologies to James Fenimore Cooper, it could have been called “The Last of the Akkadians”) who aims to kill a dreadful warlord named Memnon (Steven Brand). Memnon is a nefarious type aiming to conquer the world with the aid of a lovely sorceress (Kelly Hu), and in the process of defeating him our hero wins the girl, too. The rest of the elements of “The Scorpion King” are recycled from earlier stuff of the same sort. There’s the massive fellow who initially opposes Mathayus but becomes his steadfast supporter (Michael Clarke Duncan as Bathazar); the comic-relief cowardly sidekick (Grant Heslov as Arpid); the befuddled, eccentric old wise man (Bernard Hill as Philos); the treacherous prince (Peter Facinelli as Takmet); the over-confident general (Ralf Moeller as Thorak); and a cute, mischievous tyke (Tutu Sweeney, I think). There’s no need to detail how these characters fit together; their roles are apparent as soon as they hit the screen (and their fates are all predetermined, too). Indeed, there’s nothing remotely surprising or new in “The Scorpion King.” The script merely strings together a cascade of confrontations, chases, tongue-in-cheek asides, narrow escapes, and comic-book romantic moments; and as befits any picture featuring this star, when the makers are in doubt about what to do next, they just toss in what amounts to a flamboyant wrestling match with loincloths replacing the customary tights. (Most notable are a big battle between Mathayus and Balthazar, in which the agile giants go at one another in a manner reminiscent of the brontosaurus and T-rex in “The Lost World,” and the final fight between the hero and Memnon, in which many of the moves mimic those that fans will be familiar with from the ring.)

Still, though the whole isn’t anything more than the sum of very familiar parts, the elements have been assembled pretty well by Chuck Russell. The derring-do is decently staged, and happily the picture eschews for the most part the overabundance of effects that marred “The Mummy Returns.” That might have been to keep costs down, but the relative cheesiness of the result somehow captures the mood of old-fashioned swashbucklers better than the earlier picture did: “King” emphasizes sand, swordplay, fisticuffs and fiery sorcery over giant beasties and other threatening computer-generated phenomena, and its very homeliness has a certain simple charm redolent of an old Tarzan movie or “Conan the Barbarian.” Johnson proves a pleasant surprise, too. He’s surely got the beefiness the role requires, along with the ability to perform the stunts and feign pain; what’s surprising is that he can actually recite dialogue so that the lines sound as if they might actually come from the mouth of a human being, move in a fashion that looks reasonably natural, and even bring a knowing wink to the part without condescending to the audience. Though his range is limited, he’s certainly a distinct improvement on either Steven Seagal or Hulk Hogan, and even seems more animated and expressive than Arnold Schwarzenegger (and without the accent, too). Admittedly that’s a low bar to cross, but in terms of mere presence, The Rock is less stony than his name would imply, and that gives him a fighting chance at a screen career.

So “The Scorpion King” won’t win any awards for profundity of thought or historical accuracy; it’s just a silly, amusingly retrograde, compilation of old genre cliches. But if you go to it expecting nothing more than a modern rehash of the sort of empty-headed stuff you recall from old serials (and can take a perverse pleasure from the assortment of idiotic hairstyles it showcases), you won’t be too badly stung.