Frank Shamrock, the retired 4-time UFC champion, recently opened up about his relationship with cannabis in an interview. And while these days he may be open about his marijuana use, that wasn't always the case.

"So, I used cannabis during my entire sports career, from day one until the very end. I used to recover, I used it for pain, I used oils to protect my brain," Shamrock told High Times's Javier Hasse. "But I felt bad about it because it was illegal. So I always kept it a secret, both during my career as an athlete and then, when I became a sports broadcaster. I kept it very close to my chest until it became legal in California."

Shamrock says his time with cannabis goes back to his youth when he preferred getting high to the sometimes more disruptive effects of alcohol consumption.

"I always liked weed better than alcohol. It always made me feel better than alcohol, it was a better social medicine for me because alcohol made me goofy."

Eventually though, cannabis became his main form of treatment for the injuries he sustained as a professional fighter. Shamrock revealed he began using cannabis for that purpose after sustaining a particularly bad back injury.

"A wise chiropractor told me that if I was serious about being an athlete, this injury would cause a lot of pain, so I would have to treat it. And, for that, I would need a medicine that I could take for a long time."

That medication was marijuana, says Shamrock. Now he uses it every morning before commencing his training. The celebrated MMA fighter also admitted while he often will "vape a Volcano bag" before hitting the gym, he prefers "to smoke a joint" of good old "O.G." when he can.