Wait, didn't we already know that way, way back when some dude named Phidippides expired on the trail from Marathon to Athens at the 26-mile mark delivering some battle message.
Ah, but now, researchers in Greece have determined that hard-core marathon runners have "increased stiffness of the large arteries," suggesting that putting in the miles necessary for distance running may be bad for your heart.
OK, before everyone freaks out, consider that this is just one small study involving less than 100 people, less than half of whom were distance runners. We don't know whether this was a peer-reviewed, valid and reliable study because it's yet to be published in any journal. It was presented at the American College of Cardiology's conference in Atlanta.
Here's what the lead researcher, Dr. Despina Kardara, said in a news release:
"Regular long-term endurance training is generally beneficial for heart health, but it seems that the cardiovascular system is like a sports car engine. If you do not use it, it will decay, but if you run it too fast for too long, you might burn it out."
The most troubling data point from the study: Marathon runners scored 11 points higher on systolic blood pressure readings.
Read more about the story here, but try not to let it elevate your blood pressure.