Derny reads your heart rate, power, and cadence in real time and adjusts every target on the fly — a coach in the room, not a script on a screen.
When your heart rate climbs past its ceiling, Derny automatically lowers the intensity to bring you back — then builds again as you recover. No buttons, all ride.
Most riders never touch a setting — pick a ready-made adaptive workout, press start, and Derny adjusts to your body as you go. But if you like control, the door's right there: open the editor and write your own rules, trigger by trigger.
“If my heart rate goes above 160 for 10 seconds, drop the target by 5 watts — then hold for 30.”
You can build a rule like that by hand — or just let Derny's presets do it for you.
Effort holds no matter what. Your heart rate redlines — the workout never notices.
Effort eases as you tire, so your heart rate settles right where it should.
Everyone else rents you the app month after month. Buy Derny one time — it's yours, for every ride after.
Any FTMS smart trainer — Wahoo Kickr and beyond — plus any Bluetooth heart-rate strap. Derny drives power and resistance straight over Bluetooth, screen-locked, all ride.
Build and edit workouts by chatting with your own Claude or ChatGPT through a real, OAuth-secured connection. “Give me a 60-minute sweet-spot session that backs off if my HR climbs.” Done.
Guest-first and offline-first — it works fully signed-out with your data on your device. Sign in only if you want cloud backup and sync. No ads, no tracking, ever.
Big, honest numbers — target vs. actual power, heart rate, cadence, block progress — and a full post-ride analysis when you're done.
Derny is in active TestFlight beta on iPhone. Join, connect your trainer, and feel a workout adapt to you for the first time.