Stretch Reflexes with Special Guest Jacob Buus AndersonOctober 8, 2012
Jacob Buus Anderson, Biomedical Engineer and Associate Research Professor at the
University of Aalborg, has established himself working with multiple sclerosis patients utilizing his groundbreaking invention: the portable stretch reflex device. The man who we affectionately referred to as Tony Stark for his visionary ideas and complicated looking machinery, visited us from Denmark in June, when we had the opportunity to learn how the device works and his plans to expand it’s use to other neurological disorders.
The stretch reflex device looks like a large metal box about five feet high with cables, dials, and wires spilling out the top. It emits a sound like it is powered by hydraulics, but actually runs on an electrical motor. Jacob patiently explained that, and much more, to me one afternoon as I made sense of the science in its simplest terms.
The machine elicits and measures the stretch reflex in the soleus muscle, located in the back of the calf, throughout the step cycle. The soleus is responsible for the push-off, or plantar flexion, movement. Jacob chooses to look at the soleus because it’s only acting over the ankle joint and is therefore easy to access. When the average person lifts the foot to bring it forward (“swing phase”), the stretch reflex increases as the soleus muscle stretches and is suppressed when the foot makes contact with the ground (“stance phase”). This process does not always occur naturally in people with multiple sclerosis or spinal cord injury. Because the control signal from the brain to the spinal cord is injured or delayed, they cannot suppress the stretch reflex, and walking becomes slow, stiff, and unsynchronized. Jacob says, “Reflexes are a way to make a fast compensatory movement of muscle reflex action to keep you upright if you stumble.” I’ve wondered for years why my legs get shaky or tight when I try to quickly walk off a spasm and with one sentence, Jacob unknowingly answered my question.
Jacob explained that the feedback gained from using the device on an unaffected subject describes the physiology of step patterns. Naturally, I wondered what the goal is in eliciting the stretch reflex in people with MS or SCI if we know already know the pattern is disrupted by lack of brain/spinal cord connection. More to the point (wondered my ever-patient brain), how is this machine going to help people walk better? For one, it tells us a great deal about how the brain, spinal cord, and soleus muscle act together in coordination with movement. He can discover the contributing factors that worsen an affected person’s gait, such as the effect of certain drugs. “Finding out what’s wrong,” as Jacob put it, will hopefully only lead to changes for improvement. Furthermore, the use of this device is complementary to the reflex study Dr. Aiko Thompson conducts in the lab, which answers perhaps the most important question I asked: “Why did you come here?” (I assure you, it sounded much more diplomatic in person).
Aiko focuses on diminishing the H-reflex in the tibialis anterior muscle, located near the shin. As the soleus is responsible for plantar flexion (toes pointed downward), the TA controls dorsiflexion, wherein the toes and ankle are lifted upward. Jacob states that between the feedback of his stretch reflex device and the results that Aiko’s stretch reflex study produce, we are looking at “the complete system…the picture of how a complete nervous system is reacting.” Jacob’s interest is related to H-reflex training in that it is “one of the first things I saw that worked.” When I asked what he recommended to improve gait, he responded “reflex training.”
I am a willing subject for just about any type of research (I did the reflex training back in 2009), and Jacob’s stretch reflex device was no exception. Although my participation was not formal research, I had the honor of being the first person with SCI to use the device. Aside from the aforementioned sounds emanating from the powerful motor gear system, I had no idea what to expect when I saw the brace that looked like a close relative of an AFO (ankle-foot orthotic) that’s hinged at the ankle, the tangle of wires, a metal…thing, and a roll of duct tape. The brace is referred to as a cast, which was fitted very closely to my foot based on shoe size. The wires are Bowden cables, similar to what is used on a bicycle’s hand brakes. The cables connect to the most intriguing feature: the metal thing. It is actually a “functional joint” made of aluminum that attaches to the outside of the cast and moves along with the person’s ankle joint. The duct tape held it all together on my foot like a secure silver shoe (Jacob as the real-life brilliant Iron Man references were in full swing at this point).
Once I was hooked up and standing, I expected electrical stimulation like in the reflex study. Jacob explained it is called perturbation, which is like a disturbance to the joint. This perturbation was bending my ankle for me as I began to walk on the treadmill. He said it might feel “like hitting a stone when you walk.” I wasn’t aware of when the perturbation was coming, but I got used to it relatively quickly within the twenty-minute session. Jacob was able to regulate the system right from a nearby computer, so he could increase or decrease the perturbation as needed. It felt odd not being in total control of my usually stiff ankle, but heaviness from the cast aside, I came to appreciate the feeling of my ankle bending like it’s supposed to. It’s not an experience I’ll soon forget and although mine is complete, there are several subjects in the lab who are just beginning theirs as part of the stretch reflex study.
Jacob obviously provided us with a new perspective on the specialized area of stretch reflex study, and we enjoyed having him in the lab; Aiko even expressed how exciting it was for her to have another scientist present every day. Jacob made the most of his visit, seeing the best of what New York has to offer including museums, restaurants, Broadway shows, and baseball games. Jacob was a visitor navigating a foreign country with the added challenge of using a wheelchair (I mention this almost as an afterthought as it is irrelevant to Jacob as an engineer and person in general). He often had to wait for trains to come in on accessible platforms and once had to go to a second train station because the first one could not accommodate him. He had an unfortunate encounter with a careless taxi driver (who hasn’t?) and had to travel to from Nyack to New York several times, again dependent on unreliable transportation. These incidents may have slowed him down, but nothing stopped him. I believe my coworkers would agree that his willingness to push forward in the face of adversity left us with more than an academic lesson. That is my definition of a superhero.