“We’re interested in seeing if we can change the way people walk.”
Thor Besier, University of Auckland and MedTech Centre of Research Excellence
Sore knees are one of the curses of middle-age. But University of Auckland bioengineer Thor Besier says that the simple act of changing how we walk might be enough to stave off the need for knee surgery for many years.
As we age the cartilage in our knees can become damaged due to osteoarthritis, or from excess mechanical loading due to being overweight, for example. Thor’s research has shown that it is possible to change the mechanical loading by altering the way we walk.
A computer model sequence of the lower human body transitioning from bone to muscle. Photo: ABI University of Auckland
Thor works in the Bioengineering Institute and Department of Engineering Science at the University of Auckland, but earlier research carried out at Stanford University involved providing visual feedback to people as they walked on a treadmill in an exercise clinic. He says they used computational models to identify simple adjustments such as adding some trunk sway (“walking like a penguin”), or turning toes either in or out.
“The effect we can make with these minor adjustments can be as dramatic as having a surgery where you cut away a piece of bone … and realign the joint,” says Tor.
Although this worked very well, it relied on expensive equipment and could not be simply translated into a tool that people could use at home.
Bioengineer Thor Besier, PhD student Daniel Chen and intern Markus Haller. Photo: RNZ / Alison Ballance
Good vibrations
Thor then began investigating haptics, or tactile feedback, and developing wearable sensors.
“One of the most simple ways of providing tactile feedback is through vibrating motors, the little pager motors that you have in your cell phone.”
Thor wondered if these vibrating motors could be strategically placed on the body to provide instant feedback, and has been investigating this question with funding from a Marsden Grant.
“We’ve been investigating where we should put the motors, what type of arrangement of these motors could we use to inform or trick us into thinking we should move in a certain manner.”
PhD student Daniel Chen says he began by “looking at the different ways a human can sense touch.”
He says that by placing two vibration motors, one on each side of the foot, it was possible to make people turn left or right. However, it wasn’t possible to give more complicated feedback without people getting confused.
Next, he investigated skin stretch. Although this was an effective way of making people turn left or right, it was difficult to turn into a portable device.
So, he went back to the idea of using vibration motors to create an illusion of touch.
Prototype 'stroking' haptic gait device that is worn around the ankle and uses vibration motors, like those used in mobile phones, to give feedback on walking style. Photo: RNZ / Alison Ballance
“The device I have right now is an array of four vibration motors around the ankle, but instead of providing on-off vibration feedback you can give people stroking patterns.”
Daniel has spent the last year working out the optimal placement of vibration motors and the best phasing to give people the sensation of being stroked to the left or the right.
The effect is so intuitive that people don’t need any training. Daniel reports that people respond to it immediately with more than 90 per cent accuracy.
“That’s the good thing about this technology – people can pick it up straight away.”
He now has a prototype device, controlled by his mobile phone, which can both measure the acceleration and force of someone’s stride, and also provide directional feedback.
Smart socks
Intern Markus Haller has been working on a sister project, ‘smart socks’ that can either work on their own or be integrated with the stroking ankle bracelet.
Using soft stretchy sensors developed by StretchSense, he has built a sock that can be worn under the ankle bracelet which senses how the foot is moving.
He has had to work out how many sensors to embed in the sock and also how to integrate the sock with the ankle bracelet, but he is happy with the result.
“You can barely feel that there is anything other than a regular sock,” says Markus.
The future of wearable technology
“Wearable technology is becoming a bit of a buzz,” says Thor, “and everyone is realising that for this technology to take off it almost needs to be ubiquitous and built into the clothing.”
Thor says they are already coming up with new ideas about ways to use the stroking bracelet. After Daniel directed Markus on a complicated walk using just left and right commands from the ankle bracelet, they began to wonder if it could be used to help the visually impaired navigate.
“This is one of the great things about doing basic research, you never know where it’s going to go,” says Thor.
The next step with the haptic device is to trial it on real patients outside the clinic. A small number of clinical trials to date have shown that people can reduce the load on their joints within three weeks and reduce pain within six weeks, and Thor says it now needs to be trialled in the real world.
