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Focus on stroke: Walk with me

30 May, 2012

A few weeks ago, I went up to the Hawkshead campus of the Royal Veterinary College to meet Dr Jim Usherwood, a Wellcome Trust Research Fellow who studies locomotion, and ‘Bob’, a contraption designed to help people learn how to walk after stroke or spinal cord injuries. With me was Barry Gibb, who kindly oversaw a little filming of me in Bob’s embrace….

We met ‘Bob’ inside a large, hangar-like laboratory. He was lolling against a wall amid treadmills of varying sizes – one for horses, another for mice, even one for ducks – and other curious devices used in Dr Jim Usherwood’s research, including one for measuring the pressure of a footstep or the lift generated by a pigeon’s wing.

Tatjana Hubel, a postdoctoral researcher who works with Jim, handed me a harness and started loading Bob up with bars of lead. Essentially a seesaw on a motorised trolley, Bob has been designed to support a person who is learning to walk again. He takes some of their weight, allowing them to walk at very low speeds but with all the mechanics of normal walking. Unlike many devices used in walking rehabilitation, Bob accounts for our natural vertical movements as we walk. This characteristic bobbing, as we vault over each leg in turn, is what gave Bob his name, of course.

Once I was safely ensconced in Bob’s arms, Jim and Tatjana showed me the controls and off I went. At first, there was enough lead to support nearly all of my weight. It was very hard to walk like that, not helped by the fact that I began to think in great detail about how I was walking and when we overthink normally subconscious actions, we generally get into trouble. As Bob got faster, I stopped walking altogether, instead bouncing along like an astronaut in the moon’s low gravity. That is how Bob works: he effectively reduces the acceleration due to gravity experienced by the wearer, making them weigh less. But there is more benefit than just supporting your weight while you learn to use your legs again.

One step at a time

Gravity is what makes us fall, and falling is fundamental to walking. When you walk, each leg is like an inverted pendulum. Instead of being fixed at the top with a weight at the bottom, as in a clock, when you walk, one foot is fixed on the surface while the rest of your leg ‘swings’ over it through an arc, carrying the rest of your body. We push off with the other foot to get to the top of the arc, then gravity does the rest until our foot lands and we repeat the action on the other side.

It wouldn’t really help stroke patients to walk like an astronaut, although it was rather fun. By taking off some of the lead bars, Bob was adjusted to support less of my weight – say around half of it. This is where Bob started to show his therapeutic potential. Now I could walk, although if I went too fast, I would start doing my Neil Armstrong impression again. But actually, I could walk much more slowly than if I were carrying all of my weight.

This is vital because it would give a patient time to safely complete all of the actions that make up walking. Instead of having to get to full speed right away, which could lead to them stumbling or falling down, they can do all the right walking actions (push, vault, land, push, and so on) at a slow speed. If you tried to walk that slowly without Bob, you either wouldn’t get to the top of the arc or you would fall out of it too fast to get your other foot in place in time to land safely.

Walking normally, we are not stable at every point of a step. There are moments when it would be impossible to stop without falling over. For most of us, that’s ok – we keep moving and we are stable in motion. But if you are learning how to walk (again), you need to be able to stop and think about what you are doing from time to time. Bob would allow patients to do this.

Taking the brains out of walking

Jim is a zoologist by training, but with a soft spot for physics. He has studied how several species move themselves around, from gibbons to greyhounds, pigeons to ostriches, and not forgetting humans. Whether swinging with their arms, flapping their wings or pacing on legs, Jim analyses locomotion in order to understand why animals move the way they do. He says he takes the brains out of locomotion, which is to say, a lot of animals’ movement can be explained through passive dynamics and the basic physics of gravity.

He has applied this “no whistles or bells” approach to human walking, and to people relearning to walk too. Rehabilitation has mostly been experienced in hospitals, or elsewhere within the medical arena. Jim says medics tend to try to get people back to walking with all the whistles and bells straight away, forgetting the passive basis of our natural action. Bob is a way of enabling people to relearn walking starting at the most basic level – pushing off with one foot, vaulting over your fixed leg, and landing on the other foot. As far as Jim is concerned, swinging your arms or changing direction can come later.

Still a prototype, Bob hasn’t yet been let loose on patients. Jim is keen to test his invention but, lacking a background in clinical medicine, he needs to find a partner in the medical world – and some patients who would be happy to give it a go, of course.

It would be fascinating to know how much benefit Bob could add to walking rehabilitation. Stroke patients may have been in a hospital bed for days, even weeks, before they start rehabilitation therapies. Their muscles will be different to how they were before their stroke; the neural pathways in their brain will be different because of the damage the stroke has caused. Bob could allow them to discover a way of walking that best suits their new abilities.

Different patients may well have different walking goals – full-on walking may not be possible for all: some patients might be happy to reach a confident shuffle. And after all, confidence and independence are what Bob has really been designed to give back to patients who are struggling to walk after a spinal injury or stroke.

This article is part of the Wellcome Trust’s Focus on stroke, a series of articles, interviews and videos running throughout May 2012, which is the Stroke Association’s Action on Stroke Month.

For more information on stroke, visit the Stroke Association’s site or call its helpline on 0303 303 3100. If you or someone with you is suspected of having a stroke, call the emergency services immediately.

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