Barbells turn men into mountains because you can load the crap out of them. Throw on a few plates, and you suddenly have a bar that weighs the same as a Springbok prop. You can’t do that with a dumbbell or a kettlebell.

But if you want to work your core even harder, there might be an even better way to load the barbell, according to researchers at the University of New England.

The scientists had men perform back squats with a regularly loaded barbell. They also had them do a squat with a barbell that had weight suspended from it using resistance bands. The result: The squats done with hanging weights work the men’s cores up to 85 percent harder than the squats done with a standard barbell.

The elastic bands allowed the weights to swing back and forth and side to side. The bands also stretched and recoiled with the shifting load.

In order to perform the squat successfully under an unstable barbell, you must lock down your core to control the weight and transfer force from your legs to the bar, says Michael Lawrence, MS, lead study author.

To the untrained eye, the contraption looks like something a quack at your gym who does Shake Weight curls while standing one-legged on a Bosu ball might do. But it’s actually based on a method that powerlifters—the strongest guys on the planet—have been using to push more weight for years.

“We use a combination of bands and barbells to learn to ‘get tight’ under the bar,” says Lawrence, an Elite powerlifter. “Getting tight,” or creating tension in your muscles, signals your brain to activate more muscle so you can lift more.

“Being put under an unstable load is usually an eye opener for most unaccustomed lifters because they don’t understand how tighten their body and contract their core muscles with a normal squat,” says Lawrence. Once you can do this, though, you can more effectively control heavier loads.

You can even try the method when you bench press, which also activates your core harder and builds stronger, more resilient shoulders.

He says to work the method in with regular, heavier barbell work—unless you have questionable form. “If your squat looks like a car wreck, learn good form before you do this,” says Lawrence.

Here’s how to do it

Grab two, equally sized, full-loop resistance bands and thread them through a light plate or kettlebell.

Then loop the ends of the band around the ends of the barbell, so you have a weight dangling from each side of the bar.

Fair Warning: Go light your first reps. Once you get a feeling for how the bar moves with an unstable load, use a weight that’s equal to about half of your one rep max.

Do 3 to 5 sets of 10 to 15 reps. Once you feel comfortable, slowly up the weight.