All eyes are on the Olympics this summer, the world watching its elite athletes exceed the limits of the human body as they achieve physical greatness. No doubt it takes an unimaginable amount of blood, sweat and tears to make it to that level of physical prowess … but just how do they will themselves to push past the pain?

Researchers in Germany think they know the answer: Endorphins. After reviewing 15 studies of elite athletes and their pain tolerance, they found that those who sweat for a living have a higher tolerance for pain than mere mortals and even weekend warriors. The results, published in Pain magazine, found that while pros and non-athletes had a similar “pain threshold,” or point at which pain is felt from stimulation, pros put up with more of it. Pain tolerance varied by sport, with hard-hitting athletes like football and soccer players topping the list compared with endurance athletes. Cross-country skiers, interestingly, were the exception.

The results reinforce the previous theory that vigorous exercise increases endorphin levels not only in the blood, but also in the brain. Endorphins copy opioids and are responsible for “runner’s high.” In fact, one study found that 12 weeks of intense aerobic exercise increased one’s ability to deal with pain.

More research is needed to determine why world-class athletes can handle hurt better, but scientists suggest it’s because they are so highly motivated to push through the pain in return for money and glory. They might also have a natural ability to accept more agony.

Whether you’re training for Olympic gold or simply trying to lose a few, there’s no doubt simply staying active makes you feel like a million bucks. So even when you’re sore, stick to it, medal or no medal.