The Sports Factor

Oscar Pistorius, a double amputee who runs on carbon fibre blades, has managed to get within one second of the able-bodied qualifying time for the 100 metres sprint.

Transcript

This transcript was typed from a recording of the program. The ABC cannot guarantee its complete accuracy because of the possibility of mishearing and occasional difficulty in identifying speakers.

Now if the idea of a level playing field means anything, you'd think it would have significance in sport, I mean it's the basis of the metaphor after all.

But maybe not.

Right now there's a disabled athlete, a double amputee who runs on carbon fibre blades, who has managed to get within one second of the able-bodied qualifying time for the 100 metres sprint.

He's a South African runner named Oscar Pistorius.

He's tried and failed to get approval to run in the Olympics, but he will no doubt star in the Paralympics.

His case highlights both the extraordinary advances in prosthetics and his own remarkable competitive spirit. But that hasn't swayed opinion with the relevant international officials.

Associate Professor Tim Bach is a leading researcher in the area of biomechanics at La Trobe University. And I asked him to describe the blades on which Oscar Pistorius runs.

Tim Bach: The device is a carbon fibre laminated prosthetic foot, which is sort of shaped like a J. It attaches to a socket that the amputee fits his stump into. These devices have the capacity to flex when they're loaded and to recoil when they're unloaded.

So the idea of them is that when the athlete hits the ground running with these devices, the device flexes and stores energy, like a spring stores energy. And when the amputee takes off again, the spring recoils and returns that energy to the athlete. It behaves a little bit like the ligaments in muscles in our body, in that these tissues can store energy and allow the energy to be recovered later in the running stride.

Mick O'Regan: Indeed, and as you wrote I think in a recent article, the beginning of that 1981 Australian film 'Gallipoli' actually has the grandfather of one of the characters telling him that his legs are steel springs, and encouraging him to run as fast as he can. How should we compare the prostheses to natural legs? Are the key differences that thing about the capacity of a muscle, for example, a prostheses obviously carries no calf muscle.

Tim Bach: That's right. These carbon fibre materials are very efficient at storing energy. What we mean by that is that when energy is stored in these devices, a large portion of the energy can be recovered, about 80% of the energy. Whenever we load materials and subsequently unload them, a little bit of energy is lost as heat, and so the difference - that 80% represents the mechanical energy that's recovered, the other 20% or so is lost as heat. The body has similar energy storing structures in the ligaments and tendons.

They're less efficient at storing and recovering energy, so you might say that these prostheses are better springs, but these springs aren't attached to muscles, so that what happens in walking and running is that the spring energy is recovered as the runner takes off, but in addition to that recovered energy, there's a lot of additional energy that's added by the muscle. And so what you get out with the energy that's used to propel you forward, is much more a function of the power output by the muscle, than of the energy that's recovered from the spring.

Mick O'Regan: So rather than that recoil energy, if we look at, say, the beginning of a race, that someone with prostheses would quite literally be slower out of the blocks?

Tim Bach: Yes, they are. They don't have the same force generating potential. The spring elements are passive, they store energy that is put into them and allow recovery of some of that energy, but they can't generate force, they're not active force generators. So this puts an amputee at a big disadvantage at the start of a race and through the acceleration phases of a race. What we need to accelerate our body and get up to top speed is to apply high forces against the ground, those forces accelerate the body and the higher the force you can apply, the greater your acceleration and the sooner you reach your peak speed. The amputee is at a disadvantage because they don't have this force generating capacity in the prosthesis. And so everywhere from the start, right up until the time they achieve maximum velocity, they're at a disadvantage.

Mick O'Regan: Now the notion that Pistorius for example, or any athlete using a prosthetic limb, might be able to enhance performance by simply changing the details, lengthening the prosthesis, or changing the size or the springiness of it if you like, is that a possibility that advantage rather than coming through training and technique, could come by technical adjustment?

Tim Bach: Oh yes, it certainly is. And this is exactly what's happened with this Cheetah Flexfoot prothesis. These devices were developed in the early 1980s I think by an American fellow who is an amputee athlete, and recognised the capability of these sorts of materials to store energy and allow recovery of that energy. And there's been refinement in these devices ever since. They've refined the materials, they've changed the shape, they've changed the way they're attached to the prosthetic socket, and I think that refinements and improvements will continue. But the fact remains that they'll only ever be able to return a portion of the energy that you put into them when the foot impacts the ground. They'll never be able to allow recovery of more energy than that.

So right now the devices that are available allow recovery of about 80% of the impact energy. We might improve that to 90% or more, but it's mechanically impossible to achieve 100% recovery. So small improvements are possible, yes, but I don't think we'll see dramatic improvements.

Mick O'Regan: And indeed, I suppose just finally it throws up that old saw that at the end of the day it's more about attitude than talent. I mean what can't be measured I suppose through a series of biomechanical tests is the competitive drive, the desire to excel that someone like Oscar Pistorius obviously has.

Tim Bach: Yes. I think in the end this is just a remarkable athlete. I'd be surprised if we see the likes of him in my lifetime. He is a remarkable athlete to achieve what he has. And it's a big shame that the world won't see him, the world will see him in the Paralympics but it doesn't have the coverage or the impact that the Olympic Games does, and yes, it's disappointing for many people I think. Oscar obviously chief among them, that he won't be running in the Olympic Games.

Mick O'Regan: Biomechanics expert Tim Bach from La Trobe University.

Guests

Associate Professor Tim Bach
School of Human BioSciences, La Trobe University.

Presenter

Mick O'Regan

Producer

Andrew Davies