A decade ago, many locales offered only a handful of organized trail races. But that's not the case anymore. With a quick online search, you can find over 50 off-road races in a given location. In fact, while statistics show that road race participation continues to decline from its peak in 2014, trail racing is growing faster than ever. To find out why this long-time sport is enjoying such a surge in popularity, we talked with trail runners and advocates for the sport.