With eight wins in his past nine fights—including six knockouts—it's hard to believe Derrick Lewis has been performing at far below optimal health. 

Over the past few years, "The Black Beast" has documented his continued struggles with a back problem that plagued him before, during, and after his fights. The back pain was so severe last year that Lewis was forced to pull out of his scheduled bout against former UFC heavyweight champion Fabricio Werdum. At that time, the agony was so bad he was bound to a wheelchair.

Thankfully, Lewis got his back pain under control thanks to some shots from a doctor— pre-approved by USADA—helping him feel better on a long-term basis.

"It made a big difference," Lewis told FloCombat. "I'm always thinking that I'm going to have those problems, and it doesn't bother me at all. It's just weird what I'm going through. I've been dealing with it for years. Now that it's not even bothering me anymore, I'm always thinking it's still going to pop up sooner or later and it hasn't yet."

If the back pain wasn't enough, Lewis also revealed that blood work done ahead of his upcoming fight against Alexander Volkov Oct. 6 at UFC 229 also showed he was dealing with severely low testosterone.

There have been numerous studies over the years that looked into chronic low testosterone in endurance athletes and how extended periods of exercise has adverse effects on the endocrine system.

While Lewis isn't running marathons, it's not uncommon for mixed martial artists to endure strenuous physical exercise for multiple hours per day, several days per week—and that could potentially result in these same problems.

"I got my testosterone test done this week [with] my blood work and they told me my score was like a 399. My score is real low," Lewis said. "It's supposed to be around 1,000 or more. I've got low T, so I've got real low testosterone." 

Much like his recent breakthrough with the back pain, Lewis says his doctor has also prescribed him medication to help clear some serious blockage they believe may be able to help clear up some of the problems he's having with low testosterone.

"They have me taking some type of stuff that helps me take a crap," Lewis said. "They said I've got too much around my stomach and it's blocking the good protein to get in there. So they're making me take these pills so I can sh*t all this stuff out that's around my stomach and I can start getting the right nutrients in my body.

"My body will start burning the fat. My doctor said right now my body is not burning fat because of this."

Lewis added that he's actually felt lethargic in almost every fight he's had over the past couple years while working his way up the heavyweight rankings.

Considering he's now ranked No. 2 and arguably one win away from a title shot, Lewis has gotten there through sheer force of will. That said, he doesn't want to keep fighting that particular battle, and he hopes to regain an athletic advantage over his opponents thanks to the medical help he's received recently. 

"Even two years ago I did an interview, I believe it was after the [Shamil Abdurakhimov] fight, [and said] I don't have any energy going in there," Lewis said. "My energy level was super low. It's always low right before the fight. The only time I had high energy was before I fought Gabriel Gonzaga and whenever I fought [Damian] Grabowski—that's the only times I had high energy.

"Other than that, I'm always having low energy."

To put it all into perspective, Lewis knows he hasn't been performing anywhere near his best in his most recent fights. He hopes to show off what the marvels of modern medicine can do when he steps into the cage against Volkov. 

"I believe it was probably like 70 percent," Lewis remarked when asked about his health going into these past few fights. "No lie. Seventy percent. I haven't even really been able to train a full round or anything during camp.

"It's just crazy how much stuff that's out there since I'm in this sport and I've got to take care of my body. It's crazy. There's a lot of stuff out there. We'll see how everything plays out."