A skilled trampolinist was practicing in his backyard, when a trick went terribly wrong. Derek Therrien, 15, broke two ribs and popped a blood vessel during the mishap. The teen was into a sport called GTramp, which is becoming increasingly popular with young boys who are attempting difficult tricks on backyard trampolines. In the past, Derek performed tricks without incident, and he said this is the worst injury he’s ever had. He and his friends share videos online, trying to outperform each other.