Yes. On iOS 26, iPhone workouts can run without an Apple Watch. You can also pair sensors directly to the iPhone—for example a Bluetooth heart-rate strap. Additionally, some AirPods models can provide heart-rate data, which can also be used by the iPhone.

That said, the Apple Watch is still a great companion for convenience and for certain motion-based metrics (see below).

For running and walking workouts, Apple Watch is the most reliable way to capture step/cadence-related motion data and to make the workout easy to monitor at a glance.

Heart rate does not have to come from the Watch: you can use a Bluetooth heart-rate sensor paired to the iPhone, and (on supported models) AirPods can provide heart-rate data as well.

Virtual Treadmill: Yes. Any treadmill can be used, even if it doesn’t support FTMS. The trade-off is that speed changes must be kept in sync manually in the app.

Virtual Cycling Trainer: No. It requires an FTMS-enabled bike/trainer to control resistance and to read trainer data reliably.

No. Connecting to FTMS trainers/treadmills requires the Bluetooth connection to be established from the iPhone app. This is a platform limitation: Apple Watch has more constrained Bluetooth capabilities for this kind of device connection, and the iPhone app acts as the “host” that manages the trainer link.

Yes, but it depends on iPhone motion data quality. For cadence calculations the iPhone needs enough motion signal, so you generally need to carry/hold the iPhone in a stable way while moving.

Yes. If you connect a Bluetooth heart-rate sensor to the iPhone, the connected sensor will typically take priority when available. If needed, you can adjust this in preferences via Prefer Bluetooth heart rate sensors.

Recommendation: if you have an Apple Watch, it’s usually best to connect the heart-rate sensor to the Watch instead. watchOS will manage the sensor connection when the workout starts and can disable the Watch’s built-in heart-rate sensor—this improves accuracy and can save battery. When the sensor is connected inside the iPhone app, it can’t disable the Watch’s built-in sensor.

This usually means the app can’t detect a usable Apple Watch setup. Common causes:

• No Apple Watch is paired (or a different Watch is paired than you expect). Check Apple’s Watch app on iPhone → My Watch.
• The companion app isn’t installed on the Watch. In the Watch app on iPhone, scroll to Installed on Apple Watch / Available Apps and confirm the app is installed.
• You’re not running the iPhone app. Watch integration is supported only when the iPhone app is present, because the iPhone side is the “host”.

Things that often help:

• Make sure iPhone and Watch app versions match (updates can land on one device first).
• Check basics: Bluetooth and Wi‑Fi enabled on iPhone, Watch is unlocked, and the Watch is connected.
• If connectivity gets weird (it happens), restart both the iPhone and the Watch.
• Install the latest iOS and watchOS updates (Watch app → General → Software Update; iPhone Settings → General → Software Update). OS mismatches can cause integration issues.

If it’s still disabled, the most reliable “nuclear option” is:

1. Delete the app from the iPhone.
2. Confirm it’s removed from the Watch as well (Watch app → installed apps).
3. Install it again on the iPhone and let it reinstall on the Watch.

One more useful test: can Apple’s Fitness/Workout app start a workout on the Watch normally? If that fails too, the issue is likely broader than just this app.

Workout Effort is calculated by the system. Apps can’t force iOS/watchOS to generate it immediately. In practice, it’s usually computed when Apple’s Fitness app processes the workout.

If you need a value right away, you can manually override/enter the effort right after the workout.