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Apple Watch Heart Rate & Steps

Use your Apple Watch to supply heart rate and steps during a workout — without a chest strap, and including step counts on treadmills that don't report them.

Experimental / in testing

This is a newer feature that's still being refined. It currently lives in the experimental section of Settings, and its behavior may change between updates. The caveats below are important — please read them before relying on it.

iOS only · Premium · Apple Health

Requires an iPhone with a paired Apple Watch, an active Premium subscription, and Apple Health turned on.

What it does

When enabled, your Apple Watch starts alongside your workout and streams data back to the phone:

  • Heart rate from the watch's optical sensor — shown live on the Heart Rate card and recorded in Apple Health.
  • Steps from the watch's motion sensor — useful when your treadmill doesn't report steps of its own.

The watch records the workout in Apple Health on your behalf, so it shows up the same way a watch-tracked workout normally would.

Caveats — please read first

These are the things that most often surprise people. Understanding them up front avoids the "why didn't it work?" moment.

Keep the app open during the countdown

The watch is launched at the moment your workout starts. If the phone is locked or you leave the app while the 3-2-1 countdown is running, the watch can't start — and that workout will record normally but without any watch heart rate or steps.

Keep Treadmill Assistant open and the phone unlocked until the belt is moving. The app shows a one-time reminder if it detects this happened.

A Bluetooth heart rate strap takes priority

If you also use a Bluetooth HR monitor (chest strap or arm band), the strap takes priority for heart rate — the watch will not supply HR while the strap is connected.

Known limitation

Right now, when a strap takes over heart rate, the watch's step counting won't work either — the two are coupled. We plan to rework this so the watch can still contribute steps even when a strap supplies heart rate. For now, if you specifically want the watch's steps, don't connect a strap for that workout.

Data arrives in bursts, with a delay

The watch does not stream continuously, so what you see on the phone lags slightly behind real time:

  • Heart rate updates roughly every few seconds (about every 5 seconds). Short gaps are normal — the watch collects in bursts, and we relay exactly what it sends.
  • Steps lag and then catch up. The watch's accelerometer reports step counts in batches rather than one at a time, so the on-screen number moves in jumps and trails reality. Treat the live count as an estimate; the watch sends a final correction when the workout ends, which is the accurate figure.

We can only show what the watch measures

The app has no control over the watch's sensors — if the watch doesn't register steps or heart rate, nothing will show on the phone either.

Anything that stops your wrist from moving naturally will affect readings:

  • Resting your forearm on the treadmill console or handrail
  • Gripping the safety bar or holding on while you walk
  • Letting your hand sit on a desk or ledge

This under-counts steps and can disturb the optical heart rate reading. For the most reliable data, let your arm swing naturally as you would when walking or running outdoors.

Steps need Motion & Fitness access

Step counting relies on the watch's motion data. If steps never appear even though your arm is moving, the watch may be missing Motion & Fitness access — see Troubleshooting below.

Enabling it

  1. Open the Settings tab (gear icon).
  2. Find the experimental features section.
  3. Turn on Use Apple Watch for extra metrics.

That's it — the watch will start automatically with your next workout. Make sure your watch is on your wrist and paired.

During a workout

While the watch is coming up, the Heart Rate card walks through a couple of states:

Card shows Meaning
Waiting for watch… The phone has asked the watch to start and is waiting for it to come online.
Watch ready, waiting for HR… The watch is up and collecting; the first heart rate sample hasn't arrived yet.
A heart rate value Live data is flowing.

When the watch is your step source, the step count on the workout screen is labelled "Watch estimated" — a reminder that it updates in bursts and is finalized at the end of the workout.

Troubleshooting

"Open the watch app" / watch not reachable

Problem: The app says the Apple Watch isn't reachable, or heart rate never starts.

Solutions:

  • Make sure the watch is on your wrist and unlocked.
  • Open the Treadmill Assistant watch app manually, then start the workout again.
  • Confirm the watch is paired and within range of the phone.

Watch starts, then stops

Problem: The watch app fires up and then immediately returns to its idle screen.

Solution: This is almost always the countdown caveat above — keep the phone unlocked and the app open until the belt is moving. (A separate cause, where the first watch workout after an app restart could self-terminate, has been fixed in a recent update.)

No heart rate from the watch

Problem: Heart rate stays blank or shows another source.

Solutions:

  • If you have a Bluetooth HR strap connected, that takes priority — disconnect it if you want the watch to supply heart rate.
  • Make sure the watch is snug; a loose watch disturbs the optical sensor.
  • Let your arm move naturally rather than resting it on the console.

Steps not counted

Problem: The watch is connected but steps stay at zero or seem far too low.

Solutions:

  • Check that your arm is swinging freely — resting it on the handrail or console stops the watch registering steps.
  • If you also have an HR strap connected, the watch's steps won't work right now (see the known limitation above).
  • Grant Motion & Fitness access: on the watch this lives under the watch's privacy settings; the app also surfaces a one-time prompt pointing you to the iPhone Settings › Privacy & Security › Motion & Fitness path if access is denied.

Next steps

Need more help? Visit our Help & Support page.