In January 2007, Paralympic athlete and veteran marathon runner
Sarah Reinertsen met with a team of shoe designers from Nike
at the Nike Innovation Kitchen in Beaverton, Ore. Nike had just signed
Reinertsen, the long-time Össur athlete, in late 2006 as a sponsor and
wanted her to sit down with their design team for a meet and greet. The meeting
included Tobie and Tinker Hatfield, brothers and renowned Nike designers for
some of the most iconic and popular Nike shoes to date, from the Air Jordan III
to the Nike Free
running shoe. At the meeting in Nike’s exclusive and
overtly confidential “Kitchen,” Reinertsen showed the design team her
running leg. The Hatfield brothers, for obvious reasons, were more concerned
about the makeshift
sole she cobbled together on her running foot.
“I explained to them the process of how I created my sole and they
could not believe it,” Reinertsen told O&P Business News.
“I remember them telling me, ‘we can do better.’”
Sarah and Nike
The process, tearing apart running shoes and gluing the soles onto her
running foot, made little sense to the Nike design team. The process was made
all the more complicated when Reinertsen moved to California from New York in
2003. She regularly shipped her running foot to her prosthetist in New York to
replace the sole.
“I only have one running leg,” she said. “It’s an
expensive piece of equipment. That’s a normal case. Most amputees are
lucky to have a running leg. The shipping back and forth was costing me
valuable training time.”
Reinertsen sparked the minds of the Nike design team immediately,
especially Tobie Hatfield, who would eventually take the lead on the Sarah Sole
project, as the many prototypes were dubbed. Brainstorming in the Kitchen had
already begun. The gauntlet had been thrown down.
|Sarah Reinertsen tests her
“Why don’t we just make something that you can put on and off
and when the tread wears out you can switch it on your own?” Reinertsen
recalled one of the Nike team members asking. “No more shipping and you
won’t lose any training time.”
The Sarah Sole
Much of Nike’s innovation comes from simply listening to their
athletes and catering to their needs. The Sarah Sole was no different.
Designers and researchers from Nike’s Sports Research Lab created a
removable sole for Reinertsen to take on and off, specifically for her
marathons and sporting events.
“It was a little bit of trial and error,” Reinertsen said.
“They were constantly finding and testing new rubbers and materials. They
have an infinite amount of soles, treads and tractions to choose from. We then
had to find just the right density. We finally settled on a permutation of what
we have today.”
Reinertsen found that she could give her best feedback to Nike from
outside the lab. She started to use early versions of the Sarah Sole during
training and eventually for her competitions.
“I entered the Escape from Alcatraz marathon in San Francisco using
a newer version of the Sarah Sole,” she said. “Part of the run for
Escape is on concrete, another part of it is on a trail and then mile six or
seven is on soft sand. Runners must also climb stairs, then run back onto the
trail and back onto concrete. We finally finish on grass.”
The different terrains allowed for a different look at the suspension
and tightness of the Sarah Sole. She reported back to Nike that while running
through sand, some sand particles would get inside the foot. Researchers and
designers knew to make the sole tighter. She also noticed her fellow
“They would look at the prototype and ask how they could get
one,” Reinertsen recalled. “We needed Össur to bring it to the
market because it can serve so many people.”
A symbiotic relationship
Hilmar Janusson, vice president of research and development with
Össur, has been with the O&P company since 1993. In that time, he has
crossed paths with biomechanics from Nike. When Nike reached out to Össur
to help with the design and development of the sole a little over a year ago,
Janusson jumped at the opportunity.
“The interface between leg socket and carbon spring for running was
subject to improvement for years,” Janusson told O&P Business
News. “The next natural step is the interface with the ground. We talk
to the experts in everything that we do. After so many years, I’ve come to
know the biomechanics from Nike. When the option came to co-design the sole of
the running foot in conjunction with the improved leg, it seemed like it was a
marriage made in heaven.”
Reinertsen was the conduit between Nike’s design team and
Össur’s engineering department. She sat in on the first meeting
between Össur’s research and development team and Nike’s team
from their Kitchen. Researchers attached motion control devices on her and used
high speed video to capture and gather empirical information — just a
typical Tuesday in the Kitchen.
“What was surprising was when our team sat down with them, there
was already a common bond based on science and engineering that flowed
nicely,” Janusson said. “It’s a beautiful thing. The design
language was there, the technology was there and the ambition was there. It was
“In many instances, the optimizing of the prosthetic devices for
improving the mobility of all levels is not far from optimizing the shoes or
athletic gear for high performance athletes,” Janusson said.
“Prosthetics is all about how to deploy your energy and your forces. It is
expensive in energy terms and detrimental if you move incorrectly, ie, lots of
pain. The same applies for high performance athletes. How they interface with
the ground is highly critical to their performance. What became apparent was
their use of kinematics and motion control for application was the same way we
use it for amputees. Same principles.”
The Nike Sole
Five years after Reinersten and Nike’s initial meeting in The Kitchen,
the Nike Sole for the Össur Flex-Run foot was brought to the marketplace.
The Nike Sole consists of a midsole and outsole. The outer layer of thermal
plastic urethane, called Aeroply, interfaces between the sole and the blade.
Aeroply is made from recycled air bag units and provides additional cushioning
for the user. Nine nylon tabs wrap around the perimeter of the sole. For secure
grip, a stretchable leash pulls over a small hook insuring that the sole will
not slip off during activity. The sole clicks onto the carbon fiber foot.
“Now that the product is out there, my goal is to make sure
athletes and all amputees have access to it,” Reinertsen said. “I
want to change the perception that the Flex-Run is only for Paralympians. This
is for recreational, casual or elite runners. This is for the amputee that
wants to run their neighborhood 5K. Look at the number of people running
marathons nowadays — sometimes upwards of 20,000 people. I want to get
more amputees up and active. This is a real person’s foot.”
Moving forward, Janusson expects amputees, especially older amputees, to
have prosthetic devices specifically designed for recreational activities.
“We know an active lifestyle is important for the older amputee
population,” Janusson said. “If you think about an elderly person 15
years ago, I bet few were wearing Nike sneakers. But today, I bet most older
people have at least one pair of sneakers in their closet. I expect that to
happen in our field as well.” — by Anthony Calabro