"American Ninja Warrior" contestant Lance Pekus's wife, Heather, has been absent from the sidelines this season because of her battle with multiple sclerosis.

In TooFab's exclusive clip from Monday's episode, part one of the Season 9 finale, the couple reveals her disease to the public for the first time.

"It's hard to see the person you love just fall apart," Lance, a.k.a. the Cowboy Ninja, says in the video (above).

The Cowboy's Ninja's wife has been struggling with multiple sclerosis for the past eight to nine years, but it wasn't until a year or two ago that she started to show symptoms.

"I went from trying to run to a walker in 10 months," Heather explains. "We tried a whole bunch of medicine and treatments, but my body just doesn't respond."

"I never imagined having this, but I've always been a really positive person, and I want my kids to remember me that way," she adds.

"She's by far the toughest person I know," Lance says.

TooFab recently spoke to the athlete after his first run, where he shared his strategy to become more successful in this season's finale.

"I want to get redemption on the balance obstacles so I have to take it one obstacle at a time and look at each one as it's in front of me," he said at the time.

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