The most useful thing I learned all month was the difference between two kinds of prototypes
I spent a Saturday at Stanford as an observer at CHAT — Co-design for Health and Athlete Technology. I wasn’t old enough to participate, so I just watched. That turned out to be its own kind of useful, because when you’re not in the middle of a team trying to build something, you can pay attention to how the teams are working instead of just what they’re making.
This is what I came home thinking about.
What CHAT Is
CHAT is a one-day workshop at Stanford that brings athletes, clinicians, engineers, designers, and students into the same room to co-design technologies for human performance and recovery. The framing line on the website is creating real solutions with end-users instead of only for them.
That preposition — with instead of for — is the whole workshop in one word. Most assistive and performance technology gets designed for a population. The engineers build, the users react. Co-design flips it. The athletes are at the table from the beginning. They’re not test subjects. They’re collaborators. The team that builds the prototype includes the person who will, in some sense, live in it.
What I Watched
The athletes brought a wide range of needs into the room. Prosthetic legs. Repetitive use injuries. Other neuromotor and musculoskeletal challenges. Each design team paired with one athlete and spent the day moving from problem definition to ideation to prototype.
I watched the way you watch a sport you’re learning. I paid attention to the things that don’t show up in the final pitch. How the conversations started. Who talked first. How quickly the teams stopped pitching their own ideas and started asking the athlete questions instead. What got drawn on whiteboards versus what got built out of cardboard.
The user-driven part wasn’t a slogan. It actually changed what got designed. The teams that listened more built different prototypes than they would have built on their own. That sounds obvious when you write it down. Watching it happen is something else.
The Vocabulary That Stuck
Every team had to share a prototype at the end of the day. And here’s the concept that landed hardest for me, the one I keep using in conversations now even when I’m not talking about CHAT:
Looks-like prototypes versus acts-like prototypes.
A looks-like prototype is a representation of the final product. It shows what the thing would be. App mockups, renderings, foam models. You can hold it up and explain it.
An acts-like prototype does what the thing would do, even if it doesn’t look like the final product at all. It can be made of cardboard, tape, and parts cannibalized from other things. It doesn’t have to be pretty. It has to work — at least well enough to test the idea.
Most of the teams produced one or the other. A couple produced both. I knew the distinction existed before I went, in a vague way, but I didn’t really get it until I saw both kinds of prototypes in the same room, made by teams working on the same kind of problem.
The Wedge
The acts-like prototype that struck me the most came from a team working with an athlete who uses a prosthetic leg. The problem the athlete identified was steep hills. Climbing them on a standard prosthetic foot is mechanically rough — the foot doesn’t articulate the way a biological foot does, and the geometry works against you on an incline.
The team’s solution was a wedge that attaches to the bottom of the prosthetic foot, changing the angle so that climbing steep terrain becomes possible.
The wedge they prototyped that day was made out of a shoe. Specifically, one of the team members’ shoes. They cut it up.
I love this for a few reasons.
First, it solved the problem. Not perfectly, not for production, but well enough that the athlete could try it and the team could see whether the angle was right and whether the attachment held. That’s the entire job of an acts-like prototype.
Second, it answered a real question that a foam mockup couldn’t have answered. A foam wedge tells you what the wedge would look like. A piece of an actual shoe, attached to an actual prosthetic, on an actual incline, tells you whether the idea works. Those are different questions and they need different prototypes.
Third — and this is the part I keep coming back to — it required someone on the team to give up their shoe. That’s a small thing, but it’s also not. It means the team was willing to break their own stuff to make the athlete’s idea testable. There’s a quiet seriousness in that gesture that I don’t think gets talked about enough.
The App Mockups
Several other teams produced looks-like prototypes — phone-app mockups paired with explanations of what data the system would collect, how it would be processed, and what action the user would take based on what the screen showed.
These weren’t worse than the wedge. They were answering different questions. An app that processes biomechanical data and surfaces a recommendation is not something you can build in eight hours out of cardboard. The looks-like prototype, in that situation, is the right move. It lets the team communicate the concept, get reactions, and figure out which parts of the imagined data flow are actually plausible and which would need real engineering work to validate.
The looks-like prototype is a way of saying we believe this is the shape of the answer, and here’s enough of it to argue about.
The acts-like prototype is a way of saying we believe this is the shape of the answer, and here’s enough of it to use.
Both are real. Both have a place. The trap is mistaking one for the other — building a beautiful app mockup and thinking you’ve validated the underlying behavior, or building a working hack and thinking you’ve designed the final product. CHAT made the difference visible by putting both kinds of work side by side.
What I’m Taking Away
A few things I’m still sitting with:
Co-design is not a workshop format. It’s kind of an admission. It’s an admission that the engineer alone, no matter how skilled, doesn’t have access to the lived experience that decides whether a solution is actually useful. The athletes at CHAT weren’t there to approve designs. They were there to make them. That’s a different posture, and it produces different work.
The wedge-from-a-shoe is the kind of thing that should get celebrated more. Most of what gets shared at the end of a design event is polished. Renderings, slick slides, clean CAD. The cut-up shoe is the more honest object. It tells you that someone tried something fast, something cheap, and something that could be tested today. The aesthetic of the messy acts-like prototype is, I think, the aesthetic that actually produces change.
The vocabulary is worth keeping. Looks-like and acts-like are useful labels even outside of design. I’ve been using them in my head for other things — research ideas, project plans, even arguments. Are you describing the shape of the answer, or are you demonstrating it? Both are valid. They are not the same thing.
I’ll be old enough to participate next year. I already have ideas.
Stanford CHAT is organized by Krithika Swaminathan and Hannah O’Day. More on the workshop, including spotlights of the athlete champions and partner organizations, is at codesignhealthtech.stanford.edu.
This post is part of an ongoing research series at runlikeafish.blog exploring biomimetic approaches to assistive technology for visually impaired runners. If you’re a visually impaired runner, a guide, or a researcher working in this space, I’d love to hear from you. You can reach me at brooke@runlikeafish.blog