Whos ever had a tequila shooter? You know what you do first throw that salt over your shoulder, shouts Maureen Hagan, the incredibly charismatic vice-president of operations for GoodLife Fitness, as she energetically marches on a stage in a windowless, non-descript workout studio in Torontos east end.

Im midway through a 30-minute Flexi-Shape class, an aerobics routine involving two trademarked gadgets Ive never heard of before: a set of one-kilogram weighted cylinders (the Xco Trainers) and a five-foot-long, flexible metal rod with foam balls on each end (the Flexi-Bar). As a disco track encouraging me to feel the groove plays in the background, I frantically shake my Xcos, which are filled with a highly specialized granular substance and bear a striking resemblance to the much-spoofed Shake Weight. (Totally different science, Ms. Hagan tells me later.)

Im having fun and feeling a slight burn in my arms, yet I cant entirely, well, shake the feeling that Im on the set of a 1980s infomercial.

This 10-minute shaker routine is but an intermission from the classs main act, performing a series of arm movements with the Flexi-Bar which we hold at its midpoint and exert subtle pressure on so that it will vibrate as we squat, lunge and march.

Like David Hasselhoff, the Flexi-Bar is apparently big in Germany. Its a household name there, says Ms. Hagan. Every Olympic athlete uses it. A physiotherapist in addition to a Good Life exec and instructor, she discovered the bar at a German fitness convention and was so impressed by its effectiveness as both a rehabilitation tool (its original use) and core toner (ideal for runners and hunched-over office workers) that she implemented Flexi-Bar classes at 70 of GoodLifes 280 Canadian locations.

Based on the concept of vibration training, which sounds vaguely of the occult, the tool purportedly contracts ones muscles at a frequency thats ideal for toning. The greater the amplitude requires more muscle firing, which creates greater muscle tone, explains Ms. Hagan. And while it may seem as though your arms are doing most of the work, that actually isnt the case: To get that bar to swing, you have to brace from your core, she says. The muscles that primarily fire are those surrounding your spine.

Back in the studio with my feet firmly planted, my back straight, my shoulders back and my arms raised and slightly bent it takes a few minutes to master the movement. Its not about overgripping the bar, its about relaxing it, Ms. Hagan instructs the class, primarily women in their 30s as well as a handful of guys none of whom seem embarrassed at the prospect of looking like a slightly deranged baton twirler.

At first, Im guilty of overgripping, thrusting the bar so vigorously that Im worried Ill take flight thanks to the exuberant flapping of my batwings. (Ms. Hagan, its worth noting, has zero tricep flab.) Then, in an instant, it clicks: All thats required to keep the Flexi-Bar moving is a slight pressure, which does, ever-so-slightly, seem to originate from my core.

For the next 15 minutes, we vibrate the bar first using two hands, then alternating between left and right. Then its shaker-time, as we thrust the Xcos (the delayed movement of the granular substance is supposedly less stressful on the joints) over and back, in front and side to side.

Finally, we cool down even though Ive barely broken a sweat stretching with the Flexi-Bar to a torch singers take on Billie Jean. After a round of applause, Ms. Hagan steps off the stage and makes her way through the small crowd, high-fiving as she goes. Do you still feel your muscles vibrating? she asks. Unfortunately no, even though I really want to. (Shes that convincing.) But while I felt self-conscious and more than a little silly, being constantly prompted to keep my shoulders back improved my posture for days, which, even if my core was barely activated, had a definite slimming effect.

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Flexi-Shape: Vibrating your way to fitness