Reality Winner -- the 25-year-old federal contractor accused of leaking a classified document -- is a committed CrossFit competitor.

Winner was an animal at the gym, sometimes working out 5 times a week at Epic Ultimate Results in Augusta, GA. She even competed in the 2016 CrossFit Games Southeast regionals.

Members say they knew Winner was in the Air Force but she was vague about what she did. She was not an extrovert ... she'd say hi to folks inside, but it was all about lifting.

She was an advanced CrossFitter ... the owner says she could dead lift heavy weights.

As for whether Winner is welcome back, co-owner Glen Whelan says if she's released from custody she's welcome. As he puts it, "Until proven guilty she's not a leper."

Winner's accused of leaking a National Security Agency doc detailing Russian efforts to hack the U.S. voting system a week before the 2016 presidential election. She allegedly leaked the sensitive information to the online news outlet The Intercept.

The CrossFit franchise has gotten some backlash ... someone posted a question on its Facebook page ... whether the gym is an ISIS training camp.