Boulder Running Company co-founder Mark Plaatjes is back doing what he loves, combining his 20-year physical therapy practice with a full-service running store. And it seems fitting that his new store is just a block from the Bolder Boulder starting line. The new store, In Motion Running, just opened in a shopping plaza at 30th and Walnut streets, so more than 40,000 runners will be able to see it as they line up, wave after wave, to run Colorado’s biggest and best-known road race on Memorial Day. Plaatjes, a naturalized American from South Africa who won a gold medal in the marathon at the 1993 track and field world championships, co-founded the Boulder Running Company in 1995.