In this episode of the ‘All Things Endurance’ Podcast, host Rick Prince chats with David Callahan, Co-CEO of Ultrasignup. As the leading event registration platform for ultrarunning events, David has a unique perspective on the state and growth of ultrarunning. Some of the topics that Rick and David discuss are: 1. Could you tell our listeners a little more about your background, both professionally and athletically? 2. The popularity of ult...