By Tommy Andres, CNN
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Atlanta, Georgia (CNN) - A lot of people that show up at a bar at one in the morning are probably wrapping up an evening of drinks with friends or a date that's gone well enough to last that long.
But if you were one of the several dozen folks who rolled into The Independent in Midtown Atlanta on the Friday before Memorial Day, your night was just getting started, and drinks were not on the menu.
These brave (or crazy) men and women had paid nearly $100 bucks to stay up all night and do some of the most grueling manual labor of their lives. Oh, and they would be yelled at the whole time. This is Go Ruck.
There are tons of obstacle races out there, but Go Ruck is not a race. There are no winners. In fact, you're punished if you surpass your team.
Go Ruck is U.S. Army Special Forces training for the everyman. It's push-ups and crabwalks, swimming and simulated operations. And all of it is done wearing a backpack stuffed with 55 pounds of weights.
In fact, that backpack is what started it all. It's called the GR-1 and it was created by a former Green Beret turned entrepreneur named Jason McCarthy. He says it was inspired by the ones he used in combat:
[1:23] "Here we had this bag, right? And we spent a lot of time on it. A couple years. But yet no one wanted to buy it."
Inspired by the exploding trend of obstacle races and the sense of teamwork he felt from his service, he started Go Ruck as essentially a marketing campaign for the backpacks. And it exploded. Since the first Go Ruck challenge in 2010 more than 12,000 people have participated in countries across the world.
So why do people pay for pain? Jason says it's all about learning that you're stronger than you think.
[6:37] "I think that when you show people what they're capable of, I think it's kind of like a drug. You see the world in a different place and you say this isn't that hard. Other stuff that you're doing, it's not that hard. And this is true of life as well. So, the popularity is just based on people seeing a better side of themselves and humanity."