As the mercury drops, many New Yorkers who had been exercising outdoors during the summer — and the unusually warm early fall — will bring their routines inside. Those returning to the gym after a months-long hiatus may notice a new piece of cardiovascular equipment that looks like a cross between a treadmill and an elliptical machine. The TreadClimber by Nautilus, which is just beginning to make its way to New York-area gyms, promises an indoor workout that replicates the sensation of climbing a sand dune.

THE BASICS

At first glance, the TreadClimber resembles a treadmill, long and narrow, with sturdy, horizontal bars on either side of the console. But whereas on a treadmill, both feet step forward onto a single platform — moving in reverse — on the TreadClimber, each foot moves along its own, independently rotating mini-treadmill of sorts.

As one foot comes forward, its treadle angles upward to a maximum of 18 degrees. The incline ups the intensity of the workout, forcing the user to lift the foot, as if hiking. Since the machine comes up to meet the foot at the point of highest potential impact, the motion, like that of an elliptical machine, is easy on the knee joints.

Nautilus promises that the TreadClimber provides “the ultimate running workout at a walking pace,” and a fitness trainer, Jay Blahnik, who was demonstrating the equipment at a Nautilus-sponsored event last week, said exercising on the machine burns twice as many calories as a treadmill workout at the same pace.

THE WORKOUT

After a five-minute demonstration, I did a 20-minute walking workout on the TreadClimber in the Greenwich Village space where Mr. Blahnik and others were showing off Nautilus’s new-to-market equipment.

It was a surprisingly strenuous workout. It took me about a minute to get used to the movement of the machine and to steady myself on it, and just three minutes — going a mere 2.5 miles an hour — to break a sweat. With each foot moving on its own treadle, it soon became clear how much I favor my right side when walking. The TreadClimber forced me to even out my gait as I moved.

The motion was generally smooth, and the sand dune analogy is apt. However, at speeds exceeding 3.5 miles an hour, the TreadClimber I was on began to shake slightly — a considerable problem on a machine already moving at constantly changing angles.

WHERE TO FIND IT

New York Sports Club’s Manhattan fitness centers have Tread-Climbers, as do Long Island outposts of Gold’s Gym in Deer Park, Farmingdale, Islip, and Smithtown, and Sky Club in Hoboken. Zinn’s Gym, slated to open officially next month, on Chambers Street in TriBeCa, will also carry the machine. Home gym TreadClimber models by Bowflex, a division of Nautilus, are available at price points between $1,599 and $3,399. Unlike the commercial models, the Bowflex machines also allow the user to align and lock the consoles so that the TreadClimber works like a traditional treadmill, or to stop forward motion so the machine functions similar to a stairclimber, moving up and down only.

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