Sunita Williams will technically finish the Boston Marathon in exactly 5.4 seconds. That's because she'll be running it from inside the International Space Station (ISS), which travels at 17,000 miles per hour. If it were only that easy!

Williams will be running the race on a treadmill on board the ISS, but she'll be facing a few challenges her earthbound counterparts will never have to consider. For one, to stay put on her treadmill she needs to wear a harness that keeps her from floating away. The harness causes hip and shoulder pain, though, so she'll need to take frequent breaks. Also, when Williams sweats, the moisture doesn't evaporate like it does on Earth. Instead it just floats in the air near her body, collecting into sweaty globs.

Astronauts exercise two hours per day to keep their muscles strong while orbiting the earth, and Williams has challenged her family and friends to improve their lifestyle while she's in space. I was dragging my feet on getting out in the cold to take my walk today, but now that I've read about Sunita Williams running a marathon while hovering miles and miles above the Earth, my excuses seem more than just a little lame. Off I go!