Yes. The app is a free download and every training feature is free to use — workouts, smart-trainer control, route planning, turn-by-turn navigation, offline maps, readiness, the Apple Watch app and the web dashboard. There are no paywalled features, no trial that expires and no credit card to enter.
iPhone and iPad on iOS 18.0 or later, and Apple Watch on watchOS 11.0 or later. The watch app is optional — the iPhone app works on its own. Android and Wear OS versions are in development and have not been released.
Yes. Kardiacs drives the resistance on smart trainers and treadmills over Bluetooth using FTMS, the standard fitness-machine protocol, so each interval holds its target watts without you touching the trainer. Garmin and Tacx trainers, Wahoo trainers, heart-rate straps and power meters all connect the same way. Save a trainer, power meter, strap and watch together as a kit and they reconnect the moment you start a ride.
Yes. You download the map for your area over Wi-Fi before you leave, and after that the map draws and turn-by-turn guidance keeps calling every turn with no signal at all — on a trail, in a canyon or in a basement. Routing back to your car or your front door works offline too.
GPS coordinates, planned routes and saved addresses stay on the device — activities sync without their coordinates, and no route, start point or destination is uploaded. Daily readiness is computed on the phone from Apple Health, so nothing health-related leaves it. Playlist generation can be pointed at Apple Intelligence on your own iPhone instead of the cloud, or turned off entirely.
The Privacy Policy has the full picture.
Both. Apple Health goes both ways: workouts you recorded in other apps come in, and the sessions you do in Kardiacs are written back out. Strava activities can be synced in, and rides can be uploaded to Strava. You can also import GPX routes and export any activity as a FIT file.
It ties your profile, training history, routes, workouts and gear to an account, so they follow you onto every device you sign in to and into the web dashboard. There is no separate Kardiacs password to create. You can delete the account and everything in it at any time, from the app or the dashboard.
Yes, in the free web dashboard at app.kardiacs.com, in any browser. It holds a route planner that estimates time, work and speed from real elevation gain, head- and tailwind, tire rolling resistance and aerodynamic drag; a zone-based workout builder; your fitness and fatigue history; and the garage of bikes, kits and sensors behind both. Anything you set up there is on the phone at the next sync.
Intervals are stored as blocks of a training zone rather than fixed watts, so a workout resolves against your own fitness — your critical power and W′ — when you ride it. What it suggests each day also reads your recovery: sleep stages, heart-rate variability and stress are tracked alongside your training load, and when you are run down it steers you to an easier route or a rest day instead of another hard effort.
Yes, on the phone or in the web dashboard, down to the interval, the target and the zone. The builder previews the shape and the total, and says plainly when part of a plan is harder than your current fitness can hold. Saved workouts appear in the app's library on the next sync, ready for the trainer to drive.
Kardiacs builds each session its own mix from your own listening, matching each track's tempo to the cadence the interval is asking for — calm warm-ups, driving efforts, easy cool-downs. You can skip, favorite or stop the mix from the phone or the watch, and you can turn the feature off.
Two ways. It is free rather than subscription-funded, and it covers the whole session rather than only the indoor part — the same app runs an ERG-controlled trainer workout in your garage, navigates a road ride turn by turn, and guides a run or a walk. Kardiacs is not affiliated with Zwift, Wahoo, Garmin, Strava or Apple.
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