Sporting Speed Records
What is the fastest a human can run? See this list of 100m World Records, which tells us who is the fastest over 100m. This does not tell us who ran at the fastest speed, just who had the best average speed over that distance.
If you take the average speed of the current world 100 m record (Bolt's 9.58 s), you get about 10.44 meters/sec (23.35 miles/hr, 37.58 km/hr). However, if you were to record instantaneous speed at different points throughout the race, the runner would reach a maximum speed much greater than this. An article in the August 1996 Sports Illustrated, mentioned that Canadian Donovan Bailey reached a speed of 27.1 miles per hour (43.6 km/hr) at the 60-meter mark of his world record breaking race.
Although you would expect that over a distance of 200m the runner will slow down after achieving top speed somewhere in the first 100m, Usain Bolt's 200m world record time of 19.19 seconds works out to be an average speed of 10.42, practically the same average speed as for his 100m world record run. This is because the sprinters start from a stationary position and some time is taken up in accelerating up to top speed. In the 200m, the second 100m is covered with a running start. Over the 400m distance, the athlete continues to fatigue, and the average running speed over this distance is of course lower. Michael Johnson's WR time of 43.18 sec for the 400 meters gives a slower average time as expected, 9.3 meters/sec or 33.3 km/hr.
The highest average sprint time is achieved using the world's best time for the 150m sprint, a record also held by Bolt at 14.35 seconds. As this event is rarely run, an even better time would probably be achieved if it was raced more regularly. Average speed over this distance calculates to be 10.45 m/sec.
Split Times and Maximum Speed
Split times during sprints can gives us a better indication of top running speed. Michael Johnson's 19.32s over 200 meters earns him an average speed of 10.35 m/s, though his last 100m during this run was covered in 9.10s which gives him 10.99 m/s average. At the 1997 Athens World Championships, Maurice Green ran a wind-aided 9.86 seconds for 100 meters. In this race, 10 m split times were accurately recorded, and from this it was calculated that Green reached a top speed of 11.8 m/s.
The day after Usain Bolt's 9.58 100m world record, the IAAF released details of the split times for that race. The time for each 20m distance of the race was recorded. For Bolt, the fastest interval (60m to 80m) was run at an average speed of 44.72 km/hr (27.79 mph, 12.42 m/s).
Here's another interesting observation. In Bolt's world record run, he took 41 steps in the race, which equates to 4.28 steps per second, and an average step length of 2.44m. It would be interesting to compare this data to other great sprinters.