Inventing Iron Man (14 page)

Figure 5.2. Using the Iron Man suit of armor for extended periods could disrupt normal bodily coordination. The left panel shows angle-angle diagrams for movement of the head and torso in astronauts before spaceflight. Note the tight and small area of the plot, which means very good coordination. The right panel shows the same concept plotted for astronauts (and implied for Iron Man) after prolonged spaceflight. The coordination is much weaker. Data redrawn from Paloski (2000).

Wearing the Iron Man suit for prolonged periods would also give rise to this lessening of control of how your body would move. This means that when Tony “doffs” the suit, he better not have to do anything that requires really good coordination right away. In the case of the Iron Man suit, the effect should be fairly short-lived and represents something called an “aftereffect.” Remember the example of my running on the walkway in the airport and then the jarring experience of my landing on the hard tile surface from
chapter 2
? The effects of wearing the suit on Tony would be similar.

In addition, the effect shown in
figure 5.2
gives an indication of how someone can respond to a perturbation. Most of your motor system responses, even if you don't pay attention to them, have to do with correcting body movements when there is an external perturbation. Think about riding on a subway train or a bus as an example. When the train moves, its motion causes a sway on your body. This is a perturbation. If you don't correct for the perturbation, you step or fall. The figure here shows how the chance of not correcting properly to a perturbation after spaceflight is greatly increased.

Wearing the Iron Man suit of armor for long periods could be very much the same as the effects that would result from prolonged periods of being in space. This is where the “jelly belly” part of the title for this chapter comes from. Being in that suit would lead to extensive physical deconditioning. Especially in the later models, Tony is propelled into the air by turbines in his boots and external motors in his armor make him move. Since Tony Stark's body is in that suit, his arms and legs don't have to do much work anymore. This is why his experience is like being in space, where the reduced gravitational effects mean lower forces and less effort is needed for movement.

The force of gravity is seen as the acceleration of objects when falling (or being pulled). At sea level, this force is trying to accelerate objects at 9.81 meters per second squared, faster than many sports cars go from zero to 100 kph (60 mph). This may seem dramatic, but even while you are sitting reading this book, earth's gravitational field is trying to make your body (and the book, too, so please hold
on) fall toward the center of the earth. Fortunately, this gravitational field is countered by the activity of your muscles. Your muscles act to maintain your posture and movements, and your bones are affected to maintain their mineral density and strength. The stresses induced by the gravitational field (and your movements within that field) that strain your muscles and bones help keep you the person you are.

Without that, you would become deconditioned. Your body must also work against the inertial aspects of your body. That is, different parts of your body have different masses, and any movement you make has to work against both the desire for that part of your body to stay at rest (or in motion) as well as the constant gravitational field. If you take a two-month visit to the International Space Station, you greatly remove these effects. As a result, you lose things like strength and bone density. This was recognized as a major issue for spaceflight and a large area of research into “exercise countermeasures” while in space has developed. Astronauts must do lots of exercise and working out in order to maintain their bodies as best as possible. It's basically a case of use it or lose it. But not losing it in space remains a major challenge.

If you exercise on earth, you are usually going to get in “better” condition. But if you exercise in space you are usually not going to get in “better” condition. Rather, you will at best maintain (but usually not really) or reduce the deconditioning effects. While sporting around in a robotic suit that moves his body for him—that is, the Invincible Iron Man—won't remove all the forces acting on Tony Stark's body, it will drastically reduce the impact of them. Extensive deconditioning of Tony's body can be expected, and he needs a rigorous exercise program to maintain himself. Or he really will get a jelly belly. With so much assistance to move, he actually would wind up doing less!

Sadly, despite a childhood desire to be an astronaut, I was never able to experience being in space orbiting the earth. Sigh. However, I have walked around in a robotic pair of pants! This experience gave me an insight into how Tony might feel walking around in his suit and how disorienting it might feel to take it off again. In earlier chapters, we
saw that prosthetics help people who have lost limbs and neuroprosthetics help people when there is damage to the nervous system such as after a stroke, blast-related head injury, or spinal cord injury. In such cases, there are often many problems with being able to make normal movements, such as using the arms in tasks like reaching and using the legs during walking. Very recently neurorobotics has sprung up as a specialized field in which powered exoskeletons for assisting arm and leg movement are being used to help move the limbs with external devices. Recall these are assistive devices, well, because they assist with movement. If you have problems with movement, these neurobiotic devices provide important help. But if you can already move and have a robot amplifying your movements, it also does most of the normal movement for you too!

Starting with the shrapnel in his heart in his origin story, Tony Stark has had several health crises over the years that have resulted in his needing assistive devices. One example is in a story arc spanning Invincible Iron Man #242–245. In “Master Blaster” (Iron Man #242, 1989), Tony returns from a battle in which Iron Man once again defeats his nemesis the Mandarin. However, now as Tony Stark and wearing no armor, he is surprised to find his former girlfriend Kathleen Dar has broken into his apartment. She pulls a gun and shoots him in the chest in the last pages of that issue. We find out in the next issue and the story “Heartbeaten” that Tony is not killed by the gunshot wound but is left with a spinal cord injury. In the words of his attending physician, we learn that “the bullet's passage destroyed vital nerve tissue along the spinal column … Damage that even with today's technology is irreparable. As a result … Tony Stark will never walk again!” (By the way, I have to interject here and state that, in my opinion as a neuroscientist, all nerve tissue is vital.)

When it comes to walking and movements of the legs, a couple of devices that you can buy—almost off the shelf—are the ReWalk and the Lokomat. The ReWalk is one of the new kids on the block for commercial robotic prosthetics. It is made by Argo Medical Technologies and is a programmable robot that can be set to produce standing, stepping, and other basic movements. Lokomat is the name of a robotic assistive device produced by Hocama in Zurich, Switzerland that is basically a set of exoskeletal “pants” worn by someone and falls in the category for use in a kind of therapy called “body-weight assisted treadmill training.” Using a complex computer controller and a series of motors that can move the legs, the Lokomat
can produce stepping and walking patterns. The point of devices such as this in clinical use is to help people who have had a stroke or spinal cord injury retrain their walking pattern. After damage to the nervous system, overall muscle weakness is quite common. The Lokomat is used in walking to help support the body and then to move the limbs in patterns that are like walking.

I had the opportunity to try out the Lokomat for walking retraining by visiting the lab of a colleague, Tania Lam, at the University of British Columbia in Vancouver, Canada. Tania and I are both part of the International Collaboration on Repair Discoveries (ICORD) based in Vancouver. Research at ICORD is all about discovering cures and restoring functions for people with spinal cord injury. Tania let me walk on her treadmill set-up with the assistance of the robot. Despite knowing quite a bit about how it works, having seen the Lokomat in use many times, I had never actually climbed in and given it a try for myself. You can see an example of what this device looks like in action in
figure 5.3
. It can move the legs in a walking pattern but needs the person to be hoisted up in a body-weight support harness system (looks a bit like a parachute harness). The figure shows me getting strapped into the device that will move my hips and knees while I “walk.”

Panel A shows me just getting the harness system on; in panel B you can see that the motor system (exoskeleton) is now strapped to my legs. In panels B and C I am just being lifted off the treadmill belt slightly (see my heels lifted), and in panel D I am actually being “walked” by the Lokomat robot. It can work as a kind of passive system, where I just relax and the Lokomat “steps my legs” for me, or it can assist my attempts to step. It can even be set to resist against my normal movements. It was odd when I tried to relax and let the robot step my legs for me. It was also very difficult to do.

Related to the use of Iron Man suit and aftereffects shown in
figure 5.1
, whenever I changed “modes” on the Lokomat—for example passive to active assist to resistance—it took a number of steps to adjust to the new condition and then several steps to get used to it again when we shifted to an older condition. I guess it would be similar to feeling what it was like to walk for the first time. Or like what it is like to walk in a new scenario, such as on an icy surface in the winter, a slippery wet area, or walking along a beach in strong surf. It takes a bit to adjust to (but you can do, of course) and then a bit to “unadjust” to.

Figure 5.3. The Lokomat robotic exoskeleton. I am suspended over a treadmill and using the exoskeleton to move my legs. Things are just starting in panel A. Notice in panel B that my heels are off the ground as the harness system takes up some body weight. Panel C shows the apparatus from the back, and I am actually stepping—or being stepped by the robot—in panel D. This equipment can be used to help with walking retraining after stroke and spinal cord injury. Courtesy Tania Lam.

Back in Iron Man's world, Tony eventually reconfigures his armor so that, as described in “Yesterday … and Tomorrow” (Iron Man #244), “new servomotors and booster circuits move my legs for me! As long as I'm in this armor—I function as well as a normal man.” In this way the Iron Man suit was used to restore function that was lost, not just amplify function that Tony had. A point he clearly reflected on in “The Doctor's Passion” (Iron Man #249) when he said, “Never thought there could be such pleasure in a simple phrase like, ‘I'll walk.' But after the time I spent in a wheelchair when I was shot, just putting one foot in front of the other seems like a miracle!”

Tony's recovery might be dramatic, but it is not actually miraculous. The experience the fictional Iron Man had is similar to what occurs in real life when the nervous system adapts to changes within the body. This is called “neural plasticity,” and we will encounter it numerous times in this book. The big theme in this chapter is the use of assistive technology to amplify performance, specifically in the context of amplifying Tony Stark's abilities to produce Iron Man in action. But we are basing our discussion on examples of technology for real-life rehabilitation, such as devices like the Lokomat, which help retrain walking after spinal cord injury or stroke. This retraining of the body is directly related to neural plasticity.

Some time ago it was noticed that when a four-limbed mammal, like a cat, had a spinal cord injury that made it difficult to move, the back legs could be trained to walk again by stepping the legs on a treadmill. The animal then got better at walking. While the movement never becomes completely “normal,” it can be functional walking. This shows the ability of the nervous system to adapt and change. It is quite different from the concept of the nervous system being “hard wired” and unchangeable. Instead, the nervous system should be thought of as highly adaptable and changeable. Kind of hard wired with soft wire I guess! Going back to the specific example of walking, as in other mammals the brain and spinal cord coordinate our arms and legs together. There is strong evolutionary conservation in these connections and in the basic circuits in the brain and spinal cord that drive things like walking. We have collections of neurons called central pattern generators (or CPGs) that are evolutionarily
conserved across all species, spanning the swimming lamprey, the crustaceans, the cat, the nonhuman primates, all the way to our own species of
Homo sapiens
. CPGs are networks of neurons in the spinal cord that can generate simple walking patterns. We humans have flexible linking of CPGs responsible for each arm and leg. This is what gives us our ability to perform a variety of movements like walking, running, cycling, and swimming. In my own clinical neuroscience research, we look at how we can tap into these connections that can be broken or lost in people who have had strokes or spinal cord injuries. It seems likely that portions of the connections coordinating arms and legs can be still active after damage in stroke. This probably means that the remnants of these neural pathways can be strengthened with training. A lot of work shows that this kind of locomotor retraining can improve walking even many years or decades after injury.