Dean Karnazes is among the most extreme of extreme athletes. He has run to the South Pole, across Death Valley, and in 50 marathons in all 50 states in a span of 50 days. The latter feat, which began at the Lewis and Clark marathon in St. Charles, is documented in the film “Ultramarathon Man.” Catch it while you can. The one-time-only screening is at 7:30 p.m. Thursday at Wehrenberg’s Chesterfield Galaxy and St. Charles 18 cinemas.

Here’s the trailer: