If you're looking for a truly challenging workout in one of San Francisco's most beautiful studios, then you've got to try Bodyrok's Sculpt class.

Yes, it's hard to say "Bodyrok" without snickering, or using a classic-rock-station DJ voice. ("Coming up next, your drivetime Zepplin Bodyrok!") But your impersonations and chuckles will dry up when confronted with their Megaformer machines, long padded platforms that look like a cross between a hospital gurney and a torture device. And what delicious torture it is, as for the next 40 minutes you'll use the device in a total body workout that stretches, and possibly breaks, the limits on what you believed you could do with your core, arms, legs, and... well, pretty much everything.

If you've ever done Pilates, you're probably familiar with a lot of the movements you'll use in a Bodyrok Sculpt session; but there's a near-aerobic tempo to the class that makes it feel far fresher than a workout on the Reformer. Equally stimulating is Bodyrok's Lombard Street studio—open, airy, and filled with natural light, it's a sharp contrast to the dark, windowless rooms many of us find ourselves in as we sweat it off.

Bodyrok also made a wise decision on class size: there are 12 machines, so you'll only have 11 classmates. That's just small enough to create a sense of intimacy and individual attention, but not so small that you feel like all the attention is on you.

And you won't want too much attention, at least not at first, as the class is remarkably challenging. Friends, I'll be honest with you: I only made it through 16 minutes before I had to retire to a bench, dripping with sweat, to watch the rest of the class. Was this the result of a cold I'd fought off only two days before? My diet that day of doughnuts and coffee? Or is the class an all-new experience even for someone (like me) who clocks in more than their share of time in the weight room and on the treadmill? As much as I'd like to take the doughnut and cold excuse, I believe the last factor is the most significant.

Bodyrok's Sculpt class is a great way to get out of your current fitness rut, to challenge yourself to work harder than you have before, and to push yourself with a group of other like-minded people. However, don't let words like "challenge" and "push" scare you off — as Ashley, one of Bodyrok's instructors says, it's such a new type of workout for many people that no one's surprised if you need to ease your way into the discipline with breaks and adaptations. In fact, she said, gesturing to the other 11 members of the class "they all did, and last night they were doing the plank for five minutes." And after just 16 minutes doing what those folks were doing, that is easy to believe.

Bodyrok is located at 2128 Lombard Street, between Fillmore and Steiner Streets. You can take an introductory class for $10.

GEAR

• Close-fitting leggings are perfect, for this class -- it doesn't get hot enough for shorts, and with some of the movements, you'll want the coverage pants provide
• You'll also want a close-fitting top that won't ride or flop up, especially as you're bent over. No one wants to work out with their t-shirt in their mouth
• If you're shy about your feet, you can wear grippy socks, but bare feet will work better, and seem to be the choice of most Bodyrok Sculptors