Oscar Pistorius is a world class Olympic sprinter. He’s also a double, below-the-knee amputee. What allows him to compete is a grit that most of us can only imagine, along with a pair of Össur’s Flex-Foot Cheetah legs, J-shaped carbon fiber prostheses that fill in for feet and calves.
By now, you’ve surely heard of Össur legs and Pistorius’s watershed Olympics qualification. But what you may not know is a design problem that had to be solved first. Whereas every sprinter competes on spikes, Össur legs are smooth carbon fiber bands. So how do you affix spikes? By hand. Roughing up the surface, strong fixatives, and lots of brute force.
Even for a famous athlete of Pistorius’s resources, his spikes were a logistical nightmare that took two hours to replace. His trainers were worried about the ongoing impact of the Össur legs on his knees. And, because the spike work was totally manual, there was a lot of inconsistency on the fit of the tread (and thereby, the traction Pistorius could expect, especially during wet races).
Luckily, Pistorius is sponsored by Nike, and one of the perks of a Nike sponsorship is access to the first wave of technologically superior equipment. Tiger Woods can use prototype Nike drivers--clubs that hit farther and more controlled than others--because the top athletes in their fields get the really good stuff. For Pistorius, that meant Nike designer Tobie Hatfield chased the athlete down around the globe to create a newer, better Cheetah spike called the Nike Spike Pad.
“We were certainly able to take the learnings of spikes on shoes for 22 years, but obviously the difference is that we’re affixing it to a more immovable object, the carbon fiber blade,” Hatfield tells Co.Design. “It doesn’t articulate like a human foot does, so it was really really important for me to understand where he hit, his initial contact on the blade. Because it’s so stiff and rigid, we had to be very exact.”
So in Össur’s Iceland lab, Hatfield, along with Pistorius’s prosthetist, made Pistorius sprint again and again using Spike Pad prototypes on a pressure-sensitive treadmill--while also filming his foot strike at 500 fps. With Pistorius obviously unable to feel his feet to comment on the fit, they could only use Pistorius’s form as feedback, meaning these measurements were especially critical.
“We did that over three hours. He was pretty tired by the end,” laughs Hatfield. “I think the treadmill was fixed close to 20 mph. He’s a sprinter, not a marathon runner.”
In February, Hatfield visited Pistorius again--this time at his home in South Africa--carrying all sorts of Phylon (Nike’s branded EVA) to lessen the loads on Pistorius’s knees. Hatfield wanted the most shock absorption possible, but didn’t want Pistorius to lose launch power to a spongy pile of foam. So the resulting Spike Pad itself was fully realized then. It’s formed of a midsole--two machine-molded pieces of foam with two different densities (softer is in the back where the Pistorius lands during his stride and harder density is in the front where Pistorius begins his stride)--along with a carbon fiber Spike Plate that attaches to the bottom. But to affix it quickly for testing, Hatfield went super low tech.
“We decided to use just contact cement. We thought, anyway, that was going to be very temporary,” Hatfield explains. “I was wondering how many runs he was going to get in before starting to peel off. We found out that, it actually not only stayed on a few practices, he kept using it for months.”
As a further bonus, contact cement had another advantage over more industrial affixatives. With just a bit of heat--a mere hairdryer--the Spike Pad can be peeled from the Cheetah foot. This cut down spike replacement times from two hours to roughly fifteen minutes per leg. And Nike’s consistent production process brought much-needed predictability to Pistorius’s feet.
“Before they were shaving foams, doing all kinds of different things to get to the right thicknesses and hardnesses,” Hatfield explains. “It was arduous, took a long time and was never truly the same.”
Now, every time Pistorius launches from the starting line, it’s with an inherent confidence that his foot will always land in the same way. But the best part of the story is one easily lost in all of the tech.
“I think the cool thing about this is, it’s different than what Nike is even used to, where we make something special for our elite athletes, then we let them use it for a while before spreading it around,” Hatfield explains. “Oscar didn’t want any of that. He wanted to make sure his fellow competitors had this available to them. So we’re starting with some Nike athletes that we know--one of Oscar’s arch rivals--Jerome Singleton."
Singleton was the 2011 100m gold medalist, consistently placing as one of the top double amputee sprinters in the world. And in a few weeks, he’ll be competing against Pistorius in the Paralympic Games--on decidedly equal footing.