[Silhouette]

[2010], but fascinating all the same.

If you'd asked me how fast an elite sprinter could run today, I would probably have thought of running 100m in a little under 10s, but I don't think I would have connected that mentally with the idea that Usain Bolt runs almost as fast as a car on our 30mph streets, albeit very briefly.

[agumonkey]

I'm as astonished to think that marathon runners can sustain 20 km/h for 2 hours. 20 km/h is my average speed on bike ...