Bale and Worthington attempt to out-glower one another in “Terminator Salvation”

There was a time when watching an action movie inevitably meant turning off the brain, stuffing one’s head full of popcorn, and departing the theater with a glow of adrenaline-fueled bliss that at least lasted until you got to the parking lot. Somewhere along the line, a select few movies proved that guns and muscles didn’t have to come with a frontal lobe numbing agent. James Cameron, whatever soggy atrocities he can later be blamed for, was at the vanguard of smart action-blockbuster cinema, and the first two Terminator films (along with Aliens) are prime examples of action movies that provided a thinking man’s (and woman’s) alternative to the oeuvres of the Seagals and Van Dammes of the world. Which is why it’s so disappointing that Terminator Salvation is such a big, dumb, noisy mess.

The concept had promise. Set in the near future of 2018, the movie focuses on John Connor’s place in the early years of the human resistance to the self-aware machines that took over the planet. The film serves as both prequel and sequel, continuing the story of the war with the machines while showing how he meets Kyle Reese, the man he sends back in time to protect his mother &mdash and who will eventually become his own father. But because of the time-travel that has always underpinned the series, there’s a degree of uncertainty that the filmmakers can play with. History can be rewritten at any moment, so when a man arrives in Connor’s world naked and screaming in a thunderstorm — in what the series has established as the usual arrival method for a time traveler — it’s a great setup for suspense: Is he human? Is he machine? An assassin? A protector? Will McG pull a J.J. Abrams and not just reboot the series, but rewrite its mythology in the process?