Dr. Jaynie Yang is making strides in our understanding of how humans walk.
As a new mom many years ago, she was delighted to notice her months-old baby exhibiting a strong stepping response. When she changed the amount of weight her baby was supporting on his feet by lifting or lowering him during stepping, he changed his stepping in the same way other researchers had reported for quadrupeds, such as cats.
Yang, a professor in the Department of Physical Therapy, was intrigued by the observation, especially as it related to her specialty: the neural control of walking.
While many researchers had studied infant movement (infant stepping had long been observed), most research pertained to infant development. But Yang realized that the movement of babies could yield interesting information about how the nervous system controls walking.
"We think that because the development of the brain is still going on, and the influence of the brain on the spinal column is still quite weak compared to that in adults, what we see is more a reflection of the capabilities of the lower parts of the nervous system," says Yang. "We have found that there are remarkable similarities in the way the nervous system controls stepping in babies and other quadrupeds."
For more than 10 years, Yang has conducted studies of baby movement, often placing babies under a year old on treadmills. Since infant stepping resembles the movement of lower mammals (who can learn to walk again after spinal cord injury), her work is shedding light on the treatment of people who have sustained spinal cord injuries.
These days, Yang's research program has broadened. She's begun a series of studies on infant crawling, to explore quadrupedal co-ordination. One study compares how babies and adults coordinate their limbs during crawling.
"We're finding that adults have more flexibility with what they do when you change the speed of the treadmill belt, for instance, whereas babies stick with one form of coordination," she says.
She's also examining the many ways infants crawl. While some crawl on hands and knees, others scoot along on their bums using their feet. "There are all kinds of possibilities, which can tell us what the nervous system is capable of at that age" says Yang.
Another study examines how babies adapt in relation to novel circumstances. One research methodology involves using a split-belt treadmill, in which there are two treadmill belts, one belt running at a different speed or direction from the other. "This shows us what types of motor learning babies are capable of," says Yang.
"Our thinking is that the different methods of training do different things to the nervous system," says Yang. This might include changes to spinal reflexes or neural connections between the brain and spinal cord.
But Yang's research isn't entirely baby centred. She's presently collaborating with U of A neuroscientists Dr. Monica Gorassini and Dr. Jonathan Norton to find better ways to retrain people after spinal cord injury. Yang says more and more spinal cord injuries are incomplete, giving those individuals some sensation and limited movement in their limbs. This progression is, in part, because acute treatment for spinal injuries has improved so much, says Yang.
"Mostly we're interested in finding out, if you're training someone to walk and they're improving, what is changing in the nervous system?"
This project looks at three different methods of training: using a treadmill to give people bodyweight support as they walk on a treadmill; precision walking, which involves training people to step over obstacles or onto targets over ground ("Sort of like what you'd have to do if you were walking in the woods," says Yang); and lastly, endurance training on flat ground.
"Our thinking is that the different methods of training do different things to the nervous system," says Yang. This might include changes to spinal reflexes or neural connections between the brain and spinal cord. "Because every injury is different, we want to understand what type of injury will respond best to which type of training, and we want to know what the training is doing to the nervous system." As Yang's research endeavours expand, her team is becoming increasingly diverse.
"I think it's getting more and more interdisciplinary because of the needs of the various projects, and will likely continue this way in the future."
And even after 18 years, her research receives generous support, from funding bodies-like the Canadian Institutes for Health Research, Natural Sciences and Engineering Research Council and the Christopher and Dana Reeve Foundation-but also by a crew of eager baby volunteers. Yang says she easily recruits babies from local support groups for new moms, who are delighted to contribute to her spinal research. "We don't have time to study all the babies that want to be subjects for us."