Growth among massive, branded racing series like Tough Mudder and zombie runs is exploding. Racing used to be a straightforward affair for runners, involving little more than a bib, a stopwatch and the directive to get from the starting line to the finish line as fast as possible. Now, racing can involve escaping from zombies, getting spattered with colored powder, crawling through mud or listening to over two dozen rock bands perform along a single course. The proliferation of massive themed-racing tours is a relatively new phenomenon and might be considered a case study in economies of scale, as companies grow and improve their races. As a sport, running is experiencing tremendous growth, and these novel racing series are feeding off of the recent boom, both benefiting from the new interest in running and inspiring new athletes.