ALLENTOWN, Pa. -

The pain, agony and joy of running. More than 4,000 people hit the streets in St. Luke's annual half marathon. Many of whom ran with what's known as the "runner's high."

"Out of the body experience. Don't really feel any aches or pains just go with it, your mind is not there," female winner Heidi Peoples said.

Runners high is the sense of Euphoria runners get, allowing them to push past the point pain and fatigue.

"The body develops chemicals that work similar to narcotics like morphine," said head of Orthropedic Surgery at St. Luke's Health Network said.

As you exercise chemicals known as Endorphins are released into your brain, putting runners especially, into a zen like state.

"Once you're there you're coasting, forget about everything else just keep going," DeLong said.

This runners high dates back to primitive times. Back then cave men had to search far and wide to find food. Without those endorphins they wouldn't find much to eat. Other hypothesis state the high was gained running from predators.

Either way men's winner and Olympic hopeful Tyler Mccandless said it's a feeling everyone needs to attain at least once.

"Even if it's only 15 seconds of it and you understand what it is. Can be life changing for people," men's winner Tyler Mccandless said.

If your still in doubt you may just want to head to a finish line, one look may be all you need.