Defying Gravity With The Alter-G Treadmill

The machine that makes implausible running possible.

Written by: Sabrina Grotewold

This piece first appeared in the November issue of Competitor Magazine.

Running fast is fun. And it’s even more fun when you cheat.

I recaptured the euphoria I felt as a child, dashing around a track for 100, 200, 400 meters, nobody close to my heels, when I ran on the Alter-G, or anti-gravity, treadmill. The belt felt similar to those found on any average treadmill, but as I stepped into the neoprene shorts and zipped into the pressurized, airtight enclosure that covered the entire belt, I knew this would be no ordinary run.

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Air gushed around my legs, lifting me up slightly, as the machine calibrated my body weight. The control panel contained all of the familiar buttons of a household treadmill—time, distance and incline—but it also included up and down arrows that increase or decrease body weight in one-percent increments. Reducing my weight by as much as 80 percent within seconds of rapid air gushing and bobbing upwards meant that I could literally relive the effortless days of my track-stomping youth, when the lung-burning burden of an all-out sprint required little more than the desire to have the wind whip through my hair faster.

Cheating gravity within the safe confines of the Alter-G made it easy to want to run faster, longer. I could definitely understand why elite runners like Kara Goucher, Dathan Ritzenhein and Paula Radcliffe use the machine to log extra miles or maintain fitness while recovering from injuries.

I suffered negligible consequences—sore hamstrings the next day—after completing the day’s second run at a sub-6:00 per-mile pace for 30 minutes on the Alter-G.

Developed by NASA research scientist Robert Whalen to keep astronauts fit in space, the treadmill’s pressurized, sealed cockpit allows users to experience a low-gravity environment. The machine remained an uncommercial prototype until 2004, when Whalen’s son, Sean, a budding entrepreneur getting his master’s degree at Stanford, contacted Alberto Salazar, marathon champion and venerable coach of the Nike Oregon Project, to evaluate the treadmill. Blown away, Salazar gave Whalen $15,000 to improve the prototype. With Salazar’s input, the Whalens refined the machine, launched a business and sold their first $75,000 anti-gravity treadmill to pro basketball team, the Washington Wizards. Nike purchased three Alter-Gs as well. Recently, the Whalens are focused on the medical and rehabilitation market: In 2009, they sold 30 newer, lower cost ($24,500) machines to hospitals and physical therapy centers to help patients recover from surgeries or cope with debilitating disorders such as vertigo and diseases like Parkinson’s.

While an at-home prototype has yet to be unveiled, inquisitive runners can test the Alter-G at any number of facilities across the country—visit for details.

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