NASA astronaut Sunita Williams joined hundreds of marathon runners by participating in the Boston Marathon Monday.
Already travelling at 17,500 mph (28,162 kph), astronaut Sunita "Suni" Williams started the race on time at 10 a.m. EDT (1400 G.M.T.) with race No. 14,000 taped to the front of the treadmill.
Two laptop computers were on either side of the treadmill so she could watch a live feed of the race from Boston and keep track of where the space station was flying.
The 41-year-old Williams qualified for the Boston race by finishing the Houston Marathon in January in three hours, 29 minutes and 57 seconds.
Restrained to the treadmill in a harness so she would not float away, Williams ran at a brisk pace at the start of the 26.2-mile (42.2-kilometre) race and was confident of setting a good time and her only worry was that the station's treadmill would not function since it has had its share of breakdowns.