By Emily Chen-Newton
As summer is in full swing and temperatures in Salt Lake City rise into the 90s, Sydney Peterson is swimming, running, and rollerskiiing. She does all of this with ankle-foot orthoses (AFOs) that she designs and 3D prints herself.
Staying in shape year-round is how the two-time Winter Paralympian brings home gold—four gold medals in cross-country skiing to be exact. And when she’s not competing, she’s working towards her doctorate in neuroscience at the University of Utah.
Peterson has a genetic condition causing dystonia, involuntary muscle contractions, primarily impacting her left side. These muscle contractions have, over time, put her ankle in a fixed, inverted, and plantarflexed (pointed) position. Her ankle tendons have shortened and become stiff, forming a contracture that essentially locks her left ankle in that position. So she uses AFOs to help lift and stabilize her foot.
She says obtaining orthoses for walking or running was relatively easy through a prosthetic/orthotic clinic. But finding one for skiing was much harder. In fact, after years of pressure sores and infections from ill-fitting orthoses, it seemed nearly impossible to find one ready-made.
Very few people ski with an AFO, Peterson explains. “So there isn’t a standard solution.”
Luckily, being an adaptive athlete and working on her PhD in a rare-disease lab, Peterson is used to problems without standard solutions. Instead of waiting for the orthotic industry to come up with a cross-country skiing system, Peterson started working on a design herself.
Over about three years of trial and error, she developed her AFOs and fabricated them through a collaboration with a workshop at her university.
She begins by 3D scanning her leg and foot. Then, using a computer-aided design program, she builds a model around her anatomy.
Force-testing software estimates how the brace will respond to stress and where reinforcement is needed. She then 3D prints a prototype before moving on to the carbon fiber fabrication.
Being an adaptive athlete, she’s surrounded by what she describes as “a constant culture of adjusting and improving equipment to better match individual needs.” Peterson says, “I saw sit-skiers modifying their buckets (seats) to fit their anatomy and level of injury. On the snowboard side, athletes like Mike Schultz are building their own legs…so being around that environment made the idea feel possible.”
It was the winter of 2021 that she recalls initially needing an AFO, first for running, then for some skiing, as her symptoms worsened. By the 2022 Beijing Paralympics, she was using an orthoses for all of her skiing. She also started pairing her activities with specific devices and materials.
Peterson needs rigidity from her walking device, but for skiing, it must allow for the lateral movements that slice crisp tracks across the snow. And when she runs, she needs her system to have some energy return to bounce her down the trails.
She can also cater to her body as it changes with the ebbs and flows of a chronic condition by making adjustments to the AFO. One of her skiing AFOs uses dorsiflexion-assist hinges that help lift her foot up. She explains, “I can swap these out for stronger or weaker hinges depending on what I need.” Stronger hinges hold her foot in a more upward flexed position, which she needs. But the trade-off is “the more assistance I add, the more effort it takes from my upper leg to push against it. If the resistance is too high, it leads to fatigue pretty quickly.” Part of managing this trade-off, she’s learned, is how she uses her leg and hip muscles.
She’s also learned to think about her system as a whole. Instead of treating the AFO and ski boot as separate, she designs them to work together. She uses an orthotic element inside her ski boot to “bring the floor up” to her foot. The boot cuff itself provides lateral stability, and the AFO controls ankle flexion.
“Each component has a specific role,” and together they create a more effective system rather than “trying to make a single device do everything.”
At 24, Peterson recognizes what works for her versus what is standard. “I’ve learned not to chase ‘perfect or industry-standard’ skiing technique, but instead to focus on what’s fastest given my constraints.” Her success, she says, comes from accepting those limitations and adapting her technique around them.
