Williams goes for a jog on the Treadmill Vibration Isolation System in the space station's Zvezda Service Module. Like many things on the orbital craft, the treadmill isn't exactly like its earthbound counterpart. It's got a harness that attaches at the shoulders and the hips to keep runners from floating away.
Williams plans to use the treadmill to run along with the Boston Marathon on April 16. During the course of the marathon, Williams will circle the Earth at least twice, and while she may run as fast as 8 miles per hour, she'll fly at more than 5 miles per second.
Other astronauts use the treadmill for more basic purposes. After long periods of time in space, astronauts can be subject to bone loss--especially in their hips--because they don't walk around against the force of gravity as people on Earth do. To make sure they retain bone strength, they run on this treadmill to simulate the pounding against the ground that an earthbound runner would experience.
Photo by NASA
