Bio-Tech in Kinesiology: Innovative Strategies for Stroke Recovery
“You’re walking, and you don’t always realize it, but you’re always falling. With each step, you fall forward slightly, and then catch yourself from falling. Over and over, you’re falling, and catching yourself from falling. And this is how you can be walking and falling at the same time.”
– Laurie Anderson (writer, artist and musician)
Walking without falling is not so easy for people recovering from stroke – the leading cause of adult disabilities in the United States.
Stroke patients often succumb to additional strokes and draw huge expenses from long-term disabilities. In 2007, at least 30% of the 4.5 million stroke survivors in the United States were permanently disabled, requiring extensive and costly care, according to a 2009 report from the Wisconsin Department of Health Services' Heart Disease and Stroke Prevention Program.
In Wisconsin, 17% of stroke patients were discharged to skilled nursing facilities while another 5% were discharged with organized home health services, according to the report.
"These findings suggest an urgent need for statewide efforts to reduce the recurrence of heart attack and stroke and to improve effectiveness of cardiac and stroke rehabilitation services," the report said.
Scientists in the Kinesiology Department’s occupational therapy, motor control and biomechanics programs are responding to this call by developing innovative interventions for stroke survivors. Associate Professor Kreg Gruben focuses on balance, force and gait in leg function recovery while Associate Professor Andrea Mason and Professor Dorothy Farrar-Edwards concentrate on recovery of hand function.
Gruben Attempts to Get a Leg Up on Gait Research
People can adapt to the loss of function in one hand by using the other for many tasks of daily living but when it comes to walking, one leg cannot bear the burden alone. Therefore, stroke rehabilitation focuses on regaining leg control before hand function so that patients can at least walk again.
In an effort to help therapists better restore leg function in stroke patients, Gruben has been expanding his research on how the brain controls leg muscles during simple tasks such as pushing, and more complicated motions such as walking.
An expert on biomechanics, he designed a custom apparatus in his lab to measure the way force affects walking gait. The machine helps him identify typical walking mechanics that he hopes will inform how therapists can better rehabilitate stroke patients.
Scientists have come to understand the movement pattern of human locomotion, but precisely how and why the brain coordinates muscle forces to move in that pattern remains a mystery, Gruben said.
"We realized that we weren't going to be able to understand stroke walking because normal, healthy walking wasn't even understood," he said. "If we knew how people kept their balance during walking and standing, we would have robots that would walk and look exactly like a human … we don't know how the brain is actually coordinating things."
Gruben set out to understand locomotion mechanics, beginning with how the brain controls the forces necessary to perform basic tasks. They started with seated pushes, similar to the leg press, to determine the directions of force associated with the task. They found that the focal point of each force direction was at the subject's center of mass. But their initial results for walking appeared to tell a different story.
Gruben found that the focal point of the forces involved in walking was not at the center of mass, as scientists previously thought, but at a point above the center of mass. Gruben likened this to a solid block that, when tipped slightly, will rock back into its resting position without falling fall over.
"The higher the point, the more stable you are," Gruben said.
Furthermore, if someone was distracted or nudged while walking, the focal point would shift higher. When relaxed, the focal point was lower.
"The great thing that does is that we don't have to use as much of our brain to be stable when walking," he said. "When we get pushed or disturbed, we don't need to ask the brain to do something new to keep from tipping, it automatically rights itself."
Gruben has been applying this discovery to stroke patients, for whom balance and walking is much more complicated and prone to falling. His team began with giving stroke patients the seated pushing tasks within 24 hours of stroke before any rehab, or within months after stroke. They discovered that the focal point of force was not at the patients' center of mass, as with the control subjects, but in front of the center of mass.
"So, something stroke does makes their force go in wrong direction," Gruben said.
They correctly predicted that when stroke patients tried to walk, their focal point shifted to a location above and to the front of their center of mass, similar to toddlers learning to walk for the first time. Like toddlers, stroke patients will first flex their hips and knees, shifting the force direction closer to their center of mass. But when they try to stand up to walk without making this shift, they end up falling backwards.
"(It appears that) everybody has that particular force misdirection when we first learn to walk, and we compensate for it because, if we didn't, we'd fall over," he said. "But the compensation's really easy – bend your hips a little."
That's not so easy for stroke patients, who may need to re-learn to walk in much the same way as infants. Gruben's team predicted about 20 ways that they expected stroke patients to compensate for the force misdirection, hypotheses that matched reports of what clinicians said they witnessed in stroke patients.
"Now we're at the point where we need to start making the linkage," Gruben said. "I don't think we've got the whole picture, but I think we've got a good part of it."
Their results so far predict post-stroke behavior and therapy outcomes, which have often been unsuccessful in restoring function in patients, he said.
"Current therapy is frustratingly inefficient, mainly because it tries to remove certain behaviors which look odd, or abnormal, which according to our theory, are the appropriate things that a person should be doing to compensate for this underlying force misdirection," he said.
The literature appears to show progress in leg recovery after stroke, he said. "But do they walk normally? No."
According to the literature on walking recovery, standard rehabilitation methods haven't been able to restore normal use of the leg during walking because therapists teach patients to avoid the compensations that correct for the underlying problem of force misdirection, Gruben said.
The compensations that stroke patients perform on their own makes gait look odd and inefficient, so the therapist applies rehabilitation strategies to make gait look less odd, he said.
"According to my theory, what they're effectively doing is taking away the compensatory behaviors that are probabaly the best," he said. "When you do that, you force somebody to use a potentially less optimal compensatory strategy, albeit one that the therapist can't see as well."
Gruben said he hopes that the results of his research will help therapists better understand the underlying forces in healthy adults and stroke patients so that they can better rehabilitate their patients.
Mason Takes Rehab to Virtual Space
Assistant Professor Mason has spent the majority of her career working at the intersection of engineering and human motor control, studying how people reach, grasp and manipulate objects with their hands in both real and virtual environments.
She specifically explored how characteristics of their environment influences the ways in which people plan their movements – basic scientific research that anyone interested in human-computer interaction could use for practical applications. Recently, however, Mason started applying her discoveries to the practice of stroke recovery.
The window for stroke patients to make the most improvement with intensive rehabilitation is limited both physically and logistically. The time period that insurance covers in-patient stroke rehabilitation generally ends before patients are able to recover normal hand function. So, they rely on therapists' take-home instructions. Some therapists have recommended using video game systems that have fitness or motor control activities.
"That technology is taking off and you're seeing senior citizens who are using the Wii as a way of staying active," Mason said. "So we are interested in taking the idea of a game system and creating a rehabilitation tool for people to use in their homes."
But most of those game systems are designed for younger people, or people without disabilities. So, the idea to develop a video game specifically for stroke rehabilitation was a perfect fit for Mason's expertise. She and colleagues at UW - Oshkosh and UW - Stevens Point received a grant from UW System to develop a video game for elderly stroke survivors.
Mason has been visiting stroke support groups and senior centers to organize focus groups. Her team wants to find out what stroke survivors have problems with, what activities they would like to be able to do, what they would find engaging in a video game, and what feedback they would like out of the game that would motivate them to continue playing.
"They're out there looking for things that could potentially help them," she said. "And we think we can do it the right way because of the background that we have… we know what you're supposed to do to learn movement and we want to bring that science into the design of the game."
Mason's team is trying to take complex tasks, such as pouring something into a cup or playing cards, break them down into isolated movements, and re-apply them into a game environment. The games should allow patients to build up their ability to perform increasingly difficult tasks that they can then translate into real environments, Mason said.
The team is experimenting with ways to digitally, yet unobtrusively, capture a subject's hands and hand motions in order to represent them on a video game screen, "which actually turns out to be pretty difficult without a lot of sensors and wires," she said.
"It is really important that the game system be easy to use and not require patients to wear a lot of equipment," she said. "We feel this would be too large of a barrier for patients to actually use the game at home."
Mason and her colleagues started by trying to capture hand movements of children and healthy elderly adults and how they are different from college-age adults. But their subjects were moving so differently from the average that their sensors didn't pick up their movements. So, they have been working to overcome that challenge before applying it to the more complicated condition of paretic hands.
They also hope to incorporate a way to connect the game results to a network so that patients' therapists can access the data, monitor compliance, and give feedback to help patients get the most benefit from the system, she said.
Farrar-Edwards Tests New Technology
While scientists like Gruben and Mason develop high-tech methods for understanding and treating stroke, Professor Dorothy Farrar-Edwards focuses on assessing stroke treatments from an occupational therapy perspective.
She has partnered with colleagues in the School of Medicine and Public Health and at UW-Milwaukee on a research grant that applies brain-computer interface technology to increase recovery of hand and arm function after stroke.
But it can be a challenge to move new technologies into clinical practice, said Edwards, whose research team has been exploring the barriers to adopting new technologies for stroke recovery and patients' attitudes toward these new treatments.
So far, patients report more openness to trying new treatments than clinicians, she said.
Biomedical Engineering Associate Professor Justin Williams and his research team developed a new therapy device that combines brain activity sensors with a functional electronic stimulator (FES). The brain sensor system picks up information about the patient's activity desires and relays information to the FES which then stimulates the hand and arm muscles needed to perform a set of functional tasks.
Neuroradiology Assistant Professor Vivek Prabhakaran and his team in the School of Medicine and Public Health have been using fMRI to measure changes in the brain associated with the treatment.
Edwards and her graduate students have been assessing treatment outcomes of this device to determine whether patients can recover upper limb function after several sessions with the device.
"This new technology-based treatment promises an increased speed of recovery," Farrar-Edwards said.
The research group's goal is to show enough positive initial results to be able to secure funding for a larger, randomized control trial, she said.
At the same time, engineers at UW-Milwaukee's Rehabilitation Research Design and Disability Center (R2D2) have been developing a robotic device for stroke recovery that is designed to interact with the stimulator device that the engineers at UW-Madison have developed.
"The next phase is to marry two technologies together," Farrar-Edwards said.
Kira Luoma, an occupational therapy graduate student who has been working on the study, sees potential in the device for both additional research and wider use among practicing therapists.
She and the other students prepare the subjects by helping them stretch them out, stabilizing their arm, helping initiate movement and generally guiding the participant through the process.
"We're really important in making the participant comfortable and initiating a therapeutic relationship in such a medically-based research intervention," Luoma said.
As a future occupational therapist and occupational therapy researcher, Luoma sees promise in the new technology, based on her experience working with the patients in the pilot study.