When I first started seeing those 26.2 stickers on the backs of cars, I thought drivers were trying to brag about their gas mileage, and I judged them for it. No lie. I actually thought this. It wasn’t until I started getting into not-really-competitive-but-technically-so running myself that I figured out what it meant.

People have run for fitness and sport for a long time, but competitive, semi-competitive, and recreational road running have been gaining in popularity since the 1970s. This is largely due to increased availability of 5ks, half-marathons, “fun” runs, and “run/walks,” which have made racing more accessible and encouraged people to compete at whatever levels they feel comfortable. Running’s not just for the über fit or the seriously competitive anymore. Even the marathon — the be all, end all of most runners’ ambitions — is increasingly becoming a hobby and goal for the masses.

According to this infographic from KT Tape, more than half a millin Americans finished a marathon last year. That explains all those stickers. But as more people train for marathons, the types of injuries (and even major causes of injury, like overtraining) have remained pretty constant. Here’s a rundown of who’s running marathons today, and what they need to watch out for while they train.

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