Blade Runners and the Importance of Human-Centered Engineering
Shawn Wasserman posted on October 14, 2016 |
Altair improves prosthetics with human-centered engineering and simulation software.
Paralympian Blake Leeper talks with Altair engineers about the challenges he faces with the current blade models. Altair wanted to take a human approach to this engineering project, and to this day works closely with differently abled individuals to improve prostheses. (Image courtesy of Altair.)

Paralympian Blake Leeper talks with Altair engineers about the challenges he faces with the current blade models. Altair wanted to take a human approach to this engineering project, and to this day works closely with differently abled individuals to improve prostheses. (Image courtesy of Altair.)

When it comes to able-bodied engineers designing products for differently abled individuals, misunderstanding can lead to products that are perceived to be optimized yet actually miss the mark.

Running blades are a great example of this important concept of human-centered engineering. This is because some argue the blades offer an advantage over able-bodied runners. But when you dig deeper with a human-centered approach, you might see that this is not truly the case.

“Current running blades are incredible devices. But for every perceived advantage, there are 10 to 20 disadvantages we see with things like health, mobility, psychology and the mental game of sport,” expressed Kevin Shinn, vice president of industrial design at Altair Thinklabs. “There is not an advantage there. At the end of the day, these people are differently abled, so they will need to adapt in some way compared to able-bodied people. You have to look beyond just the device themselves, and that’s what we’ve done.”

Engineers Learn Blade Runner Challenges to Optimize the Design

Altair engineers attempt to better understand blade users by trying out the devices for themselves. The biggest challenges they faced were balance, the trampoline effect and not knowing where the ground was. (Image courtesy of Altair.)

Altair engineers attempt to better understand blade users by trying out the devices for themselves. The biggest challenges they faced were balance, the trampoline effect and not knowing where the ground was. (Image courtesy of Altair.)

The goal of human-centered engineering is less about finding solutions and more about understanding problems.

“These devices are so cool that people assume there is an advantage,” said Shinn. “Somebody with no legs with a pair of devices has an advantage. It’s kind of absurd when you think about it, but we needed to find that out to be sure and learn about the right questions to ask. To do that, we took a human-centered approach.”

Shinn's team at Altair interviewed various differently abled individuals, starting with 2012 Paralympian blade runner, Blake Leeper. The goal of these interviews was to improve understanding of the everyday routines of blade runners and how they use the product. In other words, the team wanted to try and learn about the difficulties that these super-users would face in the field in order to address them in the product's design.

The team even tried to run a few miles in their bladed shoes. They built a rig so that able-bodied people could try and run with these devices. The team didn’t even make it around the track. After a few bumps and bruises, the team noticed that their biggest challenges were balance, the trampoline effect and not feeling where the ground was.

Blade runners are top athletes who adapt to challenges that able-bodied individuals have not even dreamed of. Starting blocks aren’t designed for blades, making for an awkward start that can hurt the hips and back. In the first straight, you need to catch a rhythm as the runner doesn’t know where the ground is. In corners, blade runners lose 40 percent of their power output due to the symmetrical blade design. There is also some risk at this point of losing the blade during a run. In the back straight, the sleeve of the prosthetic starts to bunch. At this point, runners will typically be sweating heavily, increasing their risk of losing the blade once again. (Images courtesy of Altair and Leeper.)
Blade runners are top athletes who adapt to challenges that able-bodied individuals have not even dreamed of. Starting blocks aren’t designed for blades, making for an awkward start that can hurt the hips and back. In the first straight, you need to catch a rhythm as the runner doesn’t know where the ground is. In corners, blade runners lose 40 percent of their power output due to the symmetrical blade design. There is also some risk at this point of losing the blade during a run. In the back straight, the sleeve of the prosthetic starts to bunch. At this point, runners will typically be sweating heavily, increasing their risk of losing the blade once again. (Images courtesy of Altair and Leeper.)
“There are all kinds of challenges that blade runners have,” said Shinn. “The blades are symmetrical and the sole plates are flat. This can be a challenge on different substrates, around corners when running around a curve and balance is a challenge. Also, the blade runners don’t feel the ground like an able-bodied person.” 

Shinn notes that the aim is to create an equal playing field. To do that, his team focused on the human need. Some of the issues that blade runners might experience include:

  • Aerodynamics
  • Energy loss around corners
  • Connection between runner and blade
  • Balance standing and running

Altair Engineers Improve Running Blade Aerodynamics with CFD

A CFD simulation proved that the blades have significant drag (8.74 N) at the speeds Paralympic blade runners are clocked at. Altair’s team designed a sleeve (below) that reduced that drag considerably to 3.78 N. (Image courtesy of Altair.)

A CFD simulation proved that the blades have significant drag (8.74 N) at the speeds Paralympic blade runners are clocked at. Altair’s team designed a sleeve (below) that reduced that drag considerably to 3.78 N. (Image courtesy of Altair.)

The human leg isn’t flat like the blades Paralympians use when running. As a result, blade runners will experience a considerable amount of drag pulling these flat edges through the air.

“Our team looked into the aerodynamics of the blade,” explained Shinn. “We had a hypothesis that due to the flat plane on the blade that it was not aerodynamic. We put that through the virtual wind tunnel and saw there was indeed drag.”

In other words, Shinn’s team used computational fluid dynamics (CFD) to look into the drag forces a runner would experience from the blades at the speed they would be running.

“One of the things that we did was develop a shroud that moves around the blade, that can be made of different materials, that puts an aerodynamic cover of over the blade,” reported Shinn.

After an iteration cycle that tested various shroud designs, Shinn said the team developed results that can help them tune the shape quite well. The drag forces on the blade went from 8.74 newtons down to 3.78 newtons with the final shroud design.

Shinn calculates that based on these virtual wind tunnel results that runners would be able to cut their time in a 400-meter race by 0.5 seconds. This could mean the difference between a gold medal and returning home empty handed.

How Engineering Can Improve a Blade Runners’ Ability to Round Corners

When you look at your foot and the inside of your shoes, you don’t really see a flat plane. The sole of your foot contains roundness and has shapes that can help able-bodied individuals to run around corners. You don’t see those features in a running blade.

The challenges blade runners face when coming around a corner. (Image courtesy of Altair and Leeper.)
The challenges blade runners face when coming around a corner. (Image courtesy of Altair and Leeper.)
It might not seem like a lot, but Altair reports that the flat plate of a blade is enough to reduce the runner’s power output around a corner by 40 percent.

“Today’s blades have a large flat plane and are pretty symmetrical,” said Shinn. “When you are going around a corner, these blades will create a reduction of power. One solution would be to create a sole plate that is more round and dynamic. I think that is the best way to give the blades shape that would help the runners around the corner.”

Shinn explains that many blade runners will actually cut off the rubber sole of a tennis shoe and glue it onto their blades to try to improve performance. By paying attention to a user response like this, engineers can do a lot to improve the next model of a product’s design. Altair’s team created a design with a rounded heel that should help in this area.

The Connection Between Blade and Runner Can Make or Break a Race

One fear many blade runners have during a big run is that they will lose a prosthetic mid-race. This is certainly a problem that able-bodied runners aren’t even able to fathom.

Regardless of which technology the runner uses to connect their body to the blade, no one should have to deal with this fear rattling around in their brain when they are about to make the run of their life.

“How do you make the connection to something where the athlete has a sense of security?” asked Shinn. “Today, it’s done with suction and a silicone sleeve that comes over.”

One the leading causes of detachment is sweat leaking into the seal and breaking the suction. And sweat is inseparable from the art of running.

As a result, Shinn notes that the solution is to look into ways to capture the sweat before it affects the suction. This will likely result in the addition of absorbent materials to shield the human-to-blade interface.

Balance Is a Significant Engineering Challenge for Blade Runners

The Altair engineering team’s latest blade design includes a shroud to cut through the aerodynamic drag and a rounded heel to help runners around corners. Finding a way to improve the runner’s balance is still a challenge. (Image courtesy of Altair.)

The Altair engineering team’s latest blade design includes a shroud to cut through the aerodynamic drag and a rounded heel to help runners around corners. Finding a way to improve the runner’s balance is still a challenge. (Image courtesy of Altair.)

If you ever see blade runners in a video, you will see that they are constantly moving even when they are attempting to stand still. The purpose of this motion is to maintain some semblance of balance.

This isn’t too surprising when you think about it. After all, these Paralympians are essentially running on flat springs.

This constant movement results in the runners using up a lot of energy. This is energy that is essential when you are about to run the race of a lifetime.

Altair has developed a blade that has successfully tackled many of the issues that blade runners face. It includes a shroud to protect from the drag and a rounded heel to improve cornering. The team also has a good lead on addressing the moisture problem. However, the team is still working on solving the issues blade runners experience with balance.

“We’re still working on fixing this,” said Shinn. “This is especially a problem with bilateral running blades where people have dual running blades. We have a few ideas in this space and a few things on the drawing table that we hope will solve this and help these athletes conserve energy and have more balance.”

Perhaps Altair can look at including a few actuators and gyroscopes to help these runners stay stationary without exerting their own energy? However, this solution could get a little bulky and heavy, which isn’t ideal for runners.

Perhaps the talented readership from ENGINEERING.com might have some suggestions? If you do, feel free to comment below.

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