In 2015, more than 60 million Americans went for a run at least once over a 12-month period. That's roughly 20 percent of the population. And while running has certainly skyrocketed in popularity over the last several decades, it's something that people have been doing for centuries. But if there's one thing all runners have in common, it's their high likelihood of injury. According to Runners Connect, as many as 79 percent of runners get injured at least once every year. With so many runners getting hurt over the years, why is it we don't know more about running injuries and how to prevent them?

Recently, the New York Times highlighted a study on the latest trend in the running world — the super-fat running shoe — and its effect on running efficiency. The study measured the amount of oxygen a small sample of elite runners took in while running with average running shoes and maximally-cushioned running shoes. It found runners required the same amount of oxygen regardless of the shoe style. In other words, super-fat shoes don't improve or detract from running efficiency.

The logic behind maximally-cushioned running shoes is that the padding will help minimize the impact on a runner's joints, thereby preventing injury. It's a pendulum swing from the trend made popular five years ago by the book "Born to Run," in which the author argued barefoot running was the key to helping runners feel the correct alignment and foot placement they needed for injury-free running.

Immediately after that book came out, runners everywhere tossed their shoes in the trash and bolted out the door with bare feet. Soon after, toe shoes began flying off of store shelves as runners sought to adhere to the barefoot running principles without burning their feet on hot pavement. Not surprisingly, runners continued to get injured in record numbers.

Each time a new trend emerges, runners flock to the store to buy the book or the shoe or learn the trick that promises to cure what ails them. But there's a reason runners keep getting injured and it has nothing to do with science and everything to do with runners themselves. I'm not a physical therapist or a running expert. I'm just a writer who happens to run. But I've done a lot of races and met thousands of runners in real life and online, and I think most runners would agree that we are our own worst enemy when it comes to staying healthy.

Want to know why runners keep getting injured? It boils down to these three factors:

Runners are a unique bunch.

We come in all shapes, genders, ages and sizes. And each person has her own distinct style of running. Some runners hit the ground with their heels while others have a toe or midsole strike. Some runners twist at the torso while others keep the upper body straight. And for most runners, that style of running changes depending upon where, when and how fast they are running. So it's impossible for any one study to definitively determine the cause and prevention of running injuries.

Funny Running Meme Only a runner would realize this guy is not joking. (Photo: Gone For A Run)

Runners are obsessed with running.

To any logical person, pain would indicate that it's time to cut back on activity and rest. When a non-runner has pain in his foot, he puts his feet up on a cushion and grabs some ice. But runners are anything but logical. Time and time again, runners dismiss pain as part of training and try to "run through it," as if it will magically go away with more running. Not surprisingly, instead of making things better, running with pain tends to exacerbate the problem until a sore knee becomes a torn meniscus or a tightness in the lower leg becomes shin splints.

Runner are always looking for the quick-fix.

If there is anything that runners love, it's a fad. In the seven or so years I've been running I've seen barefoot running, ChiRunning, heart-rate running and now fat-shoe running — each one hailed for a few months or years as the answer to every runner's prayers for faster and better running. These running fads promise to prevent or improve running injuries and let runners do more of what they love to do — run.

But here's the thing: While researchers can't say for sure what will cause one person to get injured while running and not another, they do know what all runners can do to prevent injury. Things like stretching, massage and foam rolling loosen tight muscles before and after runs and help to improve running efficiency. Cross-training helps runners stay in shape while minimizing that pounding impact running can have on joints. And most importantly, all experts advise that runners cut back on running whenever something feels painful to keep a minor injury from becoming a major problem.

Do runners do these things? Most of them admittedly do not. So maybe the question isn't, "Why don't we know more about running injuries?'" but rather, "Why are runners so ridiculously stubborn?" That topic could be a book all by itself.