From Vision to Life-Changing Device: The Development of the Gait MyoElectric Stimulator

In late August 2004, physical therapist and researcher David Embrey, PhD, was analyzing electromyography of the gait cycle in children with and without cerebral palsy. As he stared at his screen, Embrey’s mind wandered to a conversation he’d had with a colleague about the need for innovative ways to improve gait in people with neuromuscular conditions.

Embrey looked up at the ceiling. “I’m supposed to see something, and I just don’t get it,” he said. “I give up, God.” Then, he received a vision from his computer screen – something he’d never seen. “I was given the gift of how to make an electrical stimulation system function similar to the way the normal brain functions.”

That flash of insight led, 18 years later, to the launch of the newest product to be developed with Innovation Lab: the Gait MyoElectric Stimulator (GMES). This unique functional electrical stimulation device uses dual-stimulator technology to help improve walking ability in patients with neuromuscular conditions such as stroke, cerebral palsy, multiple sclerosis and peripheral neuropathy. “What we did,” Embrey explains, “is take that innovative idea and apply it to electrical stimulation to the muscles in the lower leg, just as it happens as if it was driven from the brain, with every single step.”

Learn about the journey from concept to market-ready device in this conversation with Embrey, founder of the Research and Movement Laboratory in the Good Samaritan Children’s Therapy Unit at Mary Bridge Children’s, part of MultiCare Health System; Benjamin Dadacay, an industrial designer with Innovation Lab; and Marsha McKenna, director of clinical and market intelligence with Innovation Lab.


How does GMES differ from the way we’re currently treating foot drop, hemiplegia and other conditions your patients have? What’s the difference?

Embrey: The drop foot stimulator tries to stimulate the muscles that lift the foot, and it does so very accurately, but it doesn’t give the brain that same impulse as if you were actually letting the brain work itself.

So our system stimulates the muscles to prevent drop foot and also stimulates the calf muscles that give you the push-off. The muscles that lift are called dorsiflexors, and the muscles that push off are called plantar flexors. The dorsiflexors and plantar flexors work reciprocally – one, then the other – every step. That’s the way the brain normally functions.

If you’re just using a drop foot stimulator, all it’s doing is just helping that muscle; you’re not feeding the brain. You’re not stimulating the brain the way that muscles are stimulated during normal walking. So what we’re doing is creating an environment where the brain makes muscles function the way they’re designed to, which then helps the brain relearn what to do.

If you do the GMES stimulation for 8 to 12 weeks and walk up to an hour a day, six days a week, and then at the end of that time you take the stimulator away, our studies have shown the effects provide carryover. This suggests that the brain has learned how to function more appropriately. That’s what’s different.

How did you begin to think about how the device would work?

Embrey: My initial thought was, “How does this work for children with cerebral palsy?”, because that’s my passion. Thankfully, it also works for people who have had a stroke. That happened to be our first study. Next, our NIH-funded study showed the GMES was effective for people with peripheral artery disease, which causes cramping in their lower legs. If you stimulate the muscles correctly, it helps improve the vascular system, although we’re not exactly sure why that happens. But those are the three populations that we’ve studied. And there are half a million children with cerebral palsy, four million adults with stroke, and eight million adults with peripheral artery disease in the United States alone.

Tell me about the roles your partners played in the development of GMES.

Embrey: The first person who came on our team was an electrical engineer – Jeff Stonestreet, a retired Boeing engineer. He is a true rocket scientist. He created a way to make the first trigger mechanism, so the muscles are stimulated at the right time. Then Dr. Gad Alon, professor emeritus at the University of Maryland and a brilliant guy, said, “Ok, let’s trigger this in a different way.”

Jeff and Gad also created an electrical wave form that makes the electrical stimulation more comfortable and more efficient, as well as using less current so the batteries are smaller and last much longer. Finally, we added a single sensor with three methods (accelerometer, gyroscope and magnetometer) for triggering the muscles. These allow the muscles to fire more accurately, in a less problematic way than our first system.

Jeff and Gadi are brilliant people. It’s their knowledge, applied to the clinical environment, that allowed our team to succeed.

How did you connect with Innovation Lab?

Embrey: When it came time for me to retire, the system had not reached market. I had the prototype, the research, the patents, two Presidential Awards from MultiCare, and all the publications that go with that. But I didn’t have the regulatory piece, the marketing knowledge or financial background. And I didn’t have the funding and the engineering to get the GMES to market.

Then MultiCare decided to partner with Innovation Institute, and the Lab contacted me and said, “Let’s make this happen.”

 We met with engineers, marketing people, regulatory people and their legal people. Innovation Institute is such a gifted organization, with such a wide variety of resources, expertise and talents. And finance.

I once told a businessman, “Knowledge is power,” and he replied, “Yes, but money makes the world go ‘round.” It’s true: I knew that if the GMES couldn’t make good money for an investor and we couldn’t get the system to market, it wasn’t going to help anybody.

Marsha, how did you know GMES had strong potential for development and commercialization?

McKenna: Our clinical and market intelligence team has a rigorous process for conducting marketing assessments for new product ideas. We talked to several subject matter experts and gained insights into the clinical and market needs. One of the things we learned was that the solution needed to be affordable. From our competitive analysis, we learned that the products currently on the market were way overpriced. In addition, our subject matter experts said two-thirds of their patients couldn’t afford to have those types of devices. There is no reimbursement, so those patients who need it most cannot afford it.

We looked closely at development costs, intellectual property and barriers to entry. We also looked at the potential for GMES being used with other debilitating conditions outside of neuromuscular diseases. As a result, when we looked at all the research we conducted, the GMES device clearly had a very strong value proposition and market potential.

What did the product development phase involve?

Dadacay: Typically, innovations come in the form of an idea. But David and MultiCare came to us with a highly developed first-level prototype. We had to revalidate what they did and see what we could bring into a commercially viable product. We still followed the Product Development protocol: research, design and engineering specification assessments, human factors and user experience assessments, concept generation – which includes ideation drawing/sketching and physical prototyping, and then testing and reiterating.

We had to ensure that not only does this prototype work, but that it also takes the user into account. We wanted to design a device that users don’t see as a nuisance when they’re trying to wear it, but rather as something they will be able to use successfully and are happy to be using.

Embrey: That’s the key. Not that they just have to wear this system to function, but they want to be happy with it. I’m going to give you a couple of examples from our studies. One gentleman came into our first stroke study, and he was pretty substantially disabled and could barely function. He couldn’t walk across the room. And he said, “My goal is to walk my daughter down the aisle on her wedding day.” And he did – wearing the GMES device under his tuxedo.

When we did the study with peripheral artery disease, one gentleman couldn’t walk to his mailbox. He had to stop every few feet to let his leg cramping go away. And he was able to walk an hour nonstop when the study was finished. We got a compassionate-use exemption for him so he could continue to use GMES, which allowed him to continue his hobby: cowboy action-shooting. They walk around different obstacle courses and shoot. And he was able to win the regional competition.

Marsha, from your perspective and the Lab’s perspective, what was the big eureka moment with GMES?

McKenna: We knew this was something really important for stroke patients – to be able to possibly retrain how they walk. But when we looked at the clinical data, the other studies that Dr. Embrey had been working on, and the potential to address other debilitating conditions outside of neuromuscular disease, we felt this was a game-changer. This had the opportunity to impact patient outcomes for countless patients with a variety of other conditions. That was the point where we realized this was really something special that we wanted to be a part of.

What’s next for GMES?

McKenna: We’ve taken GMES through market analysis, and then to early validation and prototyping. Now we’re seeking commercial partners to help bring GMES to a commercial scale. We’re also evaluating a 510(k) submission to the FDA, and we’re exploring other indications outside of the neuromuscular diseases that could have a significant impact on patients’ lives.

As a result, we’re very excited to be a part of this project, because there are a lot of possibilities we want to explore. There is the potential for many people to be impacted positively by GMES and to change their lives and healthcare in ways we never imagined.


Interested in learning more about GMES? Contact Marsha McKenna at