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On freezing mountain tracks and icy slopes around the world, elite para-athletes are constantly pushing their bodies to the limit.��

But in subzero conditions, that pursuit comes with unique risks that aren’t always easy to detect.

A team of seniors in the��Biomedical Engineering Program (BME) at �鶹��Ѱ�����Boulder are working to change that by designing a residual limb warmer for winter para-athletes��during their senior capstone design course. Inspired by the ruggedness of winter jackets and ski boots, the device��will help prevent discomfort, injury and long-term complications in cold-exposed residual limbs.��

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A close look at the team's residual limb warmer design for winter para-athletes.

The project is sponsored by��, a nonprofit that partners student engineers with veterans and emergency responders to design solutions that improve their quality of life. The group says it focuses on the hidden dangers para-athletes face in extreme cold conditions, where reduced circulation and limited sensation can allow injuries to develop without warning.

“Amputated limbs often have less blood flow and less heat transfer, meaning they get cold more quickly,” said design engineer Nathan Day. “However, other factors can make the risk worse. Scar tissue buildup and a lack of nerve endings in the area could hinder the body’s natural ability to sense and respond to the cold.

“Essentially, severe tissue damage could occur without the para-athlete ever feeling it.”

To address these issues, the group created a multi-layered warming sleeve designed to enhance safety without sacrificing performance. The device uses durable wire heaters to deliver consistent heat while withstanding the impact of high-intensity crashes.

Inside the sleeve is a removable merino wool liner that sits closest to the prosthetic socket. The liner provides extra comfort and can be easily removed for cleaning after long days of use.

Beyond the inner layer, the team added a graphene reflective material that redirects heat from the wire heaters back toward the limb. Paired with lightweight synthetic insulation—similar to that used in high-performance winter gear—the system helps retain warmth even in wet or windy conditions.

And finally, the device features a rugged and weather-resistant outer shell that protects against debris and ensures continued functionality in the harsh, unpredictable environments where para-athletes compete.

“We’re not just protecting para-athletes from the cold,” said Day. “We want to empower them to conquer the mountains fearlessly.”

The team says the project was largely inspired by themselves. As Colorado natives, they were all able to draw upon some of their own experiences at mountain resorts to develop a valuable product.��

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An inside look of the residual limb warmer, showcasing the device's graphene reflective material.

But even with their own experiences on the slopes, the students quickly realized there was a critical perspective they lacked: what it truly feels like to be a para-athlete.

That’s why they teamed up with Doc Jacobs, 2026 US Para Bobsled National Champion, to provide the real-world para-athlete perspective they were missing.

“He has been an integral part of our design process this year,” said materials engineer David Debretsion. “We’ve given him our progress reports and asked him for feedback. He’s so inspiring and it’s really exciting to see how a device like this can make a real impact in his life.”

The group was able to work with a handful of other para-athletes and medical professionals, as well. According to the students, the partnerships helped open their eyes to what they call “the little things.”

“We had an idea for an LED color system to help para-athletes monitor their sleeve’s heat level, but with feedback from our sources, we realized we had to consider things like color blindness,” said product lead and design engineer Cassie Eisen. “Or even for our fastening system—we had to understand that para-athletes are wearing bulky gear that makes it difficult to use their hands.

“It’s definitely helped us take a step back and be more accessible for the greater para-athletic community.”

The team is excited to showcase their project at this year’s��Engineering Expo event. They say visitors will get the chance to interact with their physical heating sleeve, see past prototypes and even explore the different layers that make up the device.

But their journey doesn’t end there. The group will also be competing in Project S.E.R.V.E.'s National Design Competition in April, where they will put their heating sleeve to the test against 11 other universities.

Still, their goal is to create a device that doesn’t just excel on paper—it puts the para-athlete first.

“Of course, we want to win the competition,” Day said. “But this is a device that will be used on a real person for real results. Even if we don’t completely align with the needs of the competition, we’ll be happy if we create the best possible product for para-athletes.”