When I heard about this attempt, I thought "Ondrej WHO?". But it seems that almost everybody underestimated this fine athlete! 49,700 km are really fantastic, congratulations!
He was faster than Boardman from the very start of his effort, recording a time of 1'15.01 (versus 1'17.891) for the opening kilometre. He went through the 5 kilometre point over three seconds up, and by the 25 kilometre point he had extended his advantage to just under 7 seconds. This continued to grow to 18 seconds by 40 kilometres.
In his attempt, Sosenka was using a 54 x 13 gearing, a 3.2 kg wheel and 190 mm cranks, with his bike weighing a total of 9.8 kg. The reason for the heavy wheel was that although it was harder to get up to speed, it was easy to maintain it. (Remark: This paragraph was taken from an article in cyclingnews.com. Hmmm, the good old flywheel effect... But if used for track cycling, its advantage is discussed controversial. Eddy Merckx put in a huge effort to get his bike as light as possible...)
The handlebar of his bike was set very low. This allowed him to keep the arms more or less stretched out and still get a very low position. I assume that this position is much more comfortable than Boardman's - AND has aerodynamic advantages.

Check out Ondrej's website
Article in cyclingnews.com
Article in procycling
Article in Radio Prague

www.radsport-forum.de	www.radio.cz	www.sosenka.cz	www.sosenka.cz

Look at more photos on Ondrej's photogallery

Split times are taken from www.sosenka.cz/rozpis.html

One can use the split times to plot the average speed at a given distance. Boardman started quite slow, but after some kilometers with a speed around 50 km/h he reached an average speed of about 49.7 km/h. Then he went slower and slower, until his final effort pushed him to 49.441 km.
Sosenka started quite fast, he gained almost 3 seconds in the first km compared to Boardman, though he was still five seconds slower than Eddy Merckx 1972! After 10 km he marked his hightest average speed, quite close to 50 km/h. He then slowly faded to the final mark of 49.7 km/h

Now lets calculate the speed for the 5 km intervals (or 1 km intervals):
In the first 10 km Sosenka and Boardman rode almost at the same speed, but Sosenka had covered the first km 3 seconds faster, that gave him the advantage in the average speed (look above). But after 15 km Boardman faded and his speed dropped even below 49 km/h. In the last three minutes he gave it all, riding some laps with more than 51 km/h.
Sosenka's ride was much smoother, just slowly getting slower.