A paralyzed man walked again using a new groundbreaking technology
Since then, Fritz has gone to physical therapy to regain his strength and reach certain milestones, like the ability to stand in a standing frame. So when researchers stopped by the physical therapy center touting technology that could provide the ability to walk again, Fritz was intrigued.
"They were looking for physically fit volunteers with spinal cord injuries, and I ended up meeting all of their requirements," Fritz told Tech Insider.
And so began the long, arduous process of learning to walk again using brain-computer interface (BCI) technology.
When people are hooked up to BCI technology, it gives them the ability to control an external device with their mind - sort of like mastering the force or telekinesis. Originally, BCI technology was used to help people with Lou Gherig's disease communicate again, Christine King, lead author of the study Fritz participated in, told Tech Insider.
But now, researchers are looking into other ways BCI technology could be used.
People became exposed to the ways BCI could assist people with spinal cord injuries during the 2014 World Cup in Brazil, when a man paralyzed from the waist down was able to kick a ceremonial goal. He wore an exoskeleton suit that he controlled using BCI technology.
But Fritz is the first person to ever walk again using BCI technology without the assistance of robotic limbs.
How it works
People using BCI technology can either have a chip implanted into their brain or wear an electroencephalogram (EEG) cap, which presses flat metal discs against the scalp that are able to measure electrical impulses from the brain.
Because implanting a chip in the brain is so invasive, experiments are done using the EEG cap. A small amplifyer takes the feed delivered from the EEG cap and wirelessly delivers it to a computer.
The computer then uses an algorithm to suss out what signals are focused on the act of walking (or not walking, it's just as important to get the message of stopping) and ignores signals related to any other act.
The computer sends the correct signals related to to a microcontroller the person is wearing. If the person was in a robotic exoskeleton, the microcontroller will tell the suit to begin moving. In Fritz' case, the microcontroller made electrodes placed around the knees begin muscle contractions, which then began the act of walking.
Learning to walk
Before Fritz could use the technology to walk, he had to learn how to control something with his mind. Reflecting back, Fritz said this was one of the hardest, if not the hardest, part of mastering BCI technology.
"It's a hard thing to do - to sit there and think of walking," Fritz said. "So instead of trying to get the guy to walk, I tried to walk."
King said that if a person cannot get get the avatar to walk again, they probably won't be able to walk again using BCI technology.
Afterwards, Fritz practiced controlling the avatar while standing to see if he could still do it while under physical duress.
"When you're standing with a spinal cord injury, your legs and body are spasming," he said. "You have to think 'walk' and be able to focus on that and not your body."
Spinal cord injuries 'a thing of the past'?
One morning, Fritz woke up and traveled to Long Beach to attempt walking again for the first time in seven years.
When Fritz put on the EEG cap, it felt like he had put way too much gel in his hair and then covered it with a beanie (there's gel between the EEG discs to help with connectivity). He hooked himself up to the machine, but for his first try, he had on robotic legs.
He thought of walking, and saw the robotic legs begin to move over the treadmill.
Fritz didn't let himself get too excited, because the real test was to see if he could do it without robotic assistance. For the real test, he was strapped to a harness to ensure he wouldn't fall, but other than that, he was on his own.
"When taking the steps, my approach was to clear my mind, focus on each step - left foot here, right foot there," Fritz recalled. "You can feel it, not normal like, but you can feel the body react to it...like a shock to the body."
Fritz said he couldn't react to the experience right away because he had to continue concentrating in order to keep moving.
"But after the fact, it was like 'oh my gosh this actually worked,'" he said. "I was cautious with my emotions going in."
The way Fritz sees it, there's a three-horse race to restore the ability to walk in people with spinal cord injuries: BCI with exoskeletons, BCI the way he experienced it, and stem cells.
He added one isn't better than another, but that experiments coming out of the different fields seem promising.
"In my lifetime, spinal cord injuries will be a thing of the past," he said.
There will be some time before we see this technology used in day-to-day practice, but Fritz is still involved in helping the researchers refine the technology so it can be commercialized one day.
"My whole goal with this was to bring awareness to spinal cord injuries. They can happen to anyone," he said.