Running Out of This World
June 15, 2009: International Space Station astronauts are getting a new toy in August – a treadmill. Famously named after comedian Stephen Colbert1, the new running machine will help astronauts stay fit, fighting off the bone loss and muscle decay2 that otherwise comes with space travel.
Just one problem: How do you run where there's no gravity to hold your feet to the ground?
In 2007, she ran the Boston Marathon on the station station's TVIS treadmill wrapped in bungee cords for the entire 26.2 mile race.
"It's not as bad as it sounds," she laughs.
Right: Suni Williams bungeed to the TVIS treadmill onboard the ISS. [more] 
TVIS stands for "Treadmill with Vibration Isolation System." It's the space station's original treadmill, designed to allow astronauts to run without vibrating delicate microgravity science experiments in adjacent labs. COLBERT, short for "Combined Operational Load Bearing External Resistance Treadmill", has a different kind of vibration-suppression system plus some other improvements3 for runners:
"I tried a COLBERT mockup at Johnson Space Center," says Williams. "It's broader than TVIS, so you don't have to watch out where your feet go. It allows a wider, more natural gait."
Williams spent a lot of time running during her six months on board the ISS, and she recalls what it's like:
"I did this so often, it made calluses on top of my feet. Meanwhile, the calluses on the bottoms of my feet from running on Earth went away. It's totally upside down and backwards!" she laughs.
The treadmill's bungee harness "can be a bit uncomfortable," she continues. "During the marathon my foot sometimes went numb and tingly from the straps' pressure on my hip. Also, I had to use moleskin where the harness rubbed my neck raw."
And inside the close, still quarters of the space station, there are no gentle breezes to cool you down.
"Sweat globs onto you. It doesn't evaporate. I was soaking wet. During the marathon my hair was so sopping it flopped right in my face. We have little fans blowing on us but they don't do much good."
And Williams missed more than the soft winds of Earth.
"Also, one of the Soyuz astronauts floated sweet, juicy pieces of oranges to me – so refreshing!"
Right: The official patch for "COLBERT," the Combined Operational Load Bearing External Resistance Treadmill, due to launch onboard shuttle Discovery as early as August 2009. [more] 
After the grueling run, Williams longed for a hot shower. "A sponge bath just isn't the same!" she says. Neither did she have a washer and dryer for cleaning her sweat-soaked running clothes. "I hung my drenched clothes near a fan and tied my sneakers to a handrail to air them out."
Williams is the only person to have run the Boston Marathon on Earth and in space—and she noted some interesting differences:
"I recovered faster after the space marathon. When you're floating, your muscles get to rest, so you can totally relax when you finish running – it's like being in a pool."
"Also, the space marathon didn't give me the same endorphin4 effect – that wonderful mood lift runners enjoy after running – as the Earth marathon did. I'm not sure why," she says. "We are loaded with only about 60% of our Earth weight on TVIS and its harness system, so maybe I just didn't work hard enough!"
Williams says she'd consider running another marathon on COLBERT. "If another astronaut challenges my time, maybe I’ll do it. I have a competitive nature."
When it comes to running, you could say "it's out of this world."
(1) Stephen Colbert hosts Comedy Central's "The Colbert Report." NASA chose the new treadmill’s name after he entered the Node 3 naming contest, asked his fans to post the name "Colbert," and won. NASA decided to honor him instead by naming the treadmill after him.
(2) Exercise is crucial to the astronauts' wellbeing. Without gravity, crewmembers lose bone and muscle mass and their cardiovascular system weakens. By exercising on COLBERT and other exercise devices, they can counteract these effects and keep their bodies in condition.
Williams says, "We need another treadmill up there. On the station, just like at the gym, sometimes you have to wait in line. The one of us in line will ask the one on the treadmill, 'When you gonna get off? I only have 30 minutes and I need to get on there.' COLBERT will allow more astronauts to get workouts more conveniently and frequently and longer."
(3) To create COLBERT, NASA started with a medical-grade treadmill -- the same kind used in most professional sports organization to train their athletes. Modifications included nickel plating the parts, changing the sheathing of the wires, and taking the rubber off the runner surface and anodizing it to give it texture for footing. The designers also developed a vibration isolation system for the new mill to prevent upsetting delicate science experiments. In addition, the engineers reinforced the rack that will hold the new treadmill, so sans mill it weighs about 2200 pounds -- much more than the rack on station now. Heavier mass makes it absorb loads better instead of passing them on to the space station itself. They also added special springs called ‘isolators’ that absorb impact. The combination of the springs and extra mass dampens out all the vibration from running. All of this is done without using any power.
Williams says: "Up on station, COLBERT won't sit on a gyro like TEVIS does. It took me a week to get used to running on TEVIS, which kind of floats on a gyro in a pit so you don't impart loads to the station. It makes it hard to get your balance. You feel kind of like a top, with the ground moving underneath you, until you get a rhythm going and get stabilized. COLBERT won’t be on a gyro so won’t require time to get used to. You can just hop on and run. It’s stiffer and feels more stable. It will also have programs to choose from: hill workouts, intervals etc. Not just manual. That will had variety and make for some more intense workouts, which will help improve our fitness and bone density more."
(4) For more information about running and endorphins, see http://www.nytimes.com/2008/03/27/health/nutrition/27best.html
NASA's Future: US Space Exploration Policy