Intense competition among athletes isn't just happening in Tokyo this week.
Among them, a North Texas woman who has already defied the odds.
At 45-years-old Rebecca Shingledecker might be one of the fittest grandmothers in North Texas.
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Hard to believe just three years ago, Shingledecker was in a Fort Worth rehab facility relearning how to walk.
"It was unbelievable to me that I could go from this," said Shingledecker of her days of marathon running, "to this," referencing her limited movement using a walker.
Doctors discovered a golf ball-sized brain tumor in the motor control center of her brain after she had suffered four seizure-like headaches days apart.
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The surgery to remove the tumor, just 16 days after her initial diagnosis, would come with risks like loss of speech and motor control, paralysis, even death.
"I was glad to have an answer. I was also determined to fight this, so I was a little naïve about what was about to happen," said Shingledecker.
The surgery went as well as expected but then temporary paralysis set in, complicating what was already going to be a difficult road to recovery.
"From a cognitive perspective, she was thinking really slow. She had some word-finding difficulties," said Fort Worth Day Neuro Center Manager Tiffanie Morgan, with Baylor Scott & White.
However, Morgan believes her patient's undeterred attitude made all the difference.
"She maintained that attitude of "I'm going to get back to what I love to do and she was able to do that," said Morgan.
The road to recovery didn't get easier.
Shingledecker quickly regained her strength at the gym while attending outpatient rehab, but six months later, she suffered another brain injury in a car accident.
Six months after that, a third head injury at the gym.
The tattoo on her leg illustrates how she made her miraculous comeback.
"It says, 'take the sourest lemon life has to offer and turn it into something resembling lemonade.' It just means to me that life can throw you some bad experiences and you don't have control over that but what you do have control over is what you do with it," said Shingledecker.
She is competing as a neuromuscular athlete in the newly formed adaptive division of the games, a division designed for athletes who've overcome medical challenges or disabilities.