Ptacnik qualified for the Czech squad in two track cycling events at the 2008 Summer Olympics in Beijing by receiving one of the team's three available berths based on UCI's selection process from the Track World Rankings. In the men's team sprint, held on the first day of the program, Ptacnik and his teammates Babek and Spicka battled in an opening heat against the U.S. trio of Michael Blatchford, Giddeon Massie, and Adam Duvendeck with an eleventh-place time in 45.678 and an average speed of 59.109 km/h, failing to advance further to the top eight match round. Two days later, in the men's sprint, Ptacnik narrowly missed out the round-of-sixteen matchup by a four-thousandth second margin on the morning prelims in 10.569, finishing nineteenth overall in the process.