Derny reads your heart rate, power, and cadence as you ride, and moves the target when your body asks for it. The workout follows you.
When your heart rate climbs past its ceiling, Derny lowers the intensity and brings you back. As you recover, it builds again. You never touch a button.
Most riders never touch a setting. Pick a ready-made adaptive workout, press start, and Derny adjusts to your body as you go. If you like control, 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.”
That’s a rule you write yourself, in plain fields. Or let the presets do the writing.
Effort holds no matter what. Your heart rate redlines and the workout never notices.
Effort eases as you tire, so your heart rate settles right where it should.
Every beta rider gets the whole app: every workout, every adaptive rule, nothing held back.
FTMS is the open Bluetooth standard nearly every modern smart trainer speaks, whatever badge is on it. Derny drives power and resistance straight over Bluetooth, screen locked, all ride. Pair any Bluetooth heart-rate strap alongside.
Connect your account once. Every finished ride uploads itself, with power, heart rate, and cadence. There’s nothing to export and nothing to remember after you unclip.
Build and edit workouts by chatting with your own Claude or ChatGPT. The connection is OAuth-secured. Ask for a 60-minute sweet-spot workout that backs off when your heart rate climbs, and it lands in your library.
Derny 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.
FTMS is the open Bluetooth standard for smart trainers, and it’s what Derny talks. Every trainer that supports it is driven the same way, with no partnership and no per-brand hacks. Riding something that isn’t listed? If it pairs as a controllable smart trainer over Bluetooth, it almost certainly works.
See full trainer compatibility →Pair your Bluetooth trainer and heart-rate monitor, then ride with power, heart rate, cadence, and adaptation in view. Afterward, the recorded stream becomes a detailed ride analysis.
The beta is live on iPhone via TestFlight, and opening up on Android. Pick your phone, connect your trainer, and feel a workout adapt to you for the first time.