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Keely and Polar Flow, for the same Loop.
Keely and Polar Flow are both free apps for the Polar Loop, and the band works with one of them at a time. Polar Flow is Polar’s own app, with Nightly Recharge, Sleep Plus Stages, Cardio Load, training sessions, a five-minute fitness test and integrations such as Strava and Apple Health. Keely turns the same band into one Recovery score, a Load target for the day, live stress, your sleep need, a VO2 max from your walks and runs and Keely Age, and keeps your raw heart data on your iPhone.
Updated
At a glance
| Keely | Polar Flow | |
|---|---|---|
| Price | Free | Free |
| Morning | Recovery: one score, 0–100 %, with each of its five inputs shown | Nightly Recharge: a status in six levels, with an ANS charge (−10 to +10) and a sleep charge |
| Training | Load by heart-rate zone, a target range each morning, and Balance | Cardio Load (TRIMP), strain against tolerance, and four load statuses |
| Stress | Live, 0–100, still or moving | No stress score for the Loop |
| Sleep | Stages from the Loop, need (goal, debt and a hard day), consistency and a lights-out time | Sleep Plus Stages with a sleep score (1–100), and SleepWise alertness |
| VO2 max | From your walks and runs: their pace in Apple Health against the Loop’s heart rate, with bands for your age and sex | The Polar Fitness Test: five minutes lying still, from resting heart rate, HRV, your details and how you rate your training |
| An age | Keely Age, from your VO2 max, each Monday | Not listed for the Loop |
| Skin temperature | Part of Recovery, against your normal | Not shown for the Loop |
| Workouts | Found in your heart rate and classed by zones | Automatic detection, or start a session with your phone’s GPS; 170+ sport profiles |
| Formulas | Every input, weight and constant is published | Methods described in Polar’s own guides and white papers |
| Your data | Raw heart data stays on your iPhone; your account backs up daily summaries | Synced to your Polar account and flow.polar.com |
| Integrations | Apple Health: saves your sleep, workouts, resting heart rate and breathing rate, and reads your walks and runs for Fitness | Strava, TrainingPeaks, Apple Health and Google Health |
| Export | Not yet | Sessions as GPX, TCX, CSV or FIT, and an account download without activity and sleep data |
Facts about Polar Flow come from Polar’s own pages, checked October 5, 2026.
Where Polar Flow does more
- Training sessions. Start one from the app with your phone’s GPS, pick from 170+ sport profiles, and hear voice guidance as you go.
- A VO2 max without a walk or run. The Polar Fitness Test takes five minutes lying still; Polar suggests it about once a month. Keely estimates VO2 max only from walks and runs that another app or watch saves to Apple Health.
- Integrations. Strava, TrainingPeaks, Apple Health and Google Health, all through your Polar account.
- A web dashboard and export. flow.polar.com, with Nightly Recharge reports since September 2026, and your sessions as GPX, TCX, CSV or FIT.
- Trends in the diary. Since Flow 7.37.0 (September 28, 2026), up to three graphs of the past two weeks, from Cardio Load to HRV during sleep.
- Activity goals and an inactivity alert after 55 minutes of sitting.
- Polar’s own guidance. Nightly Recharge, SleepWise and Training Load Pro, which Polar documents in its guides.
Where Keely is different
- One number each morning. Recovery is a single score from 0 to 100 %, and tapping it shows each input as helping, holding back or normal. See Recovery.
- A target for the day. Load sets a range each morning from your Recovery and your last four weeks, so you know when to push and when to hold back. See Load.
- Live stress. From 0 to 100 while Keely is open, and read from heart rate alone while you move. See Stress.
- VO2 max from effort. Keely reads the pace of your steady walks and runs against the Loop’s heart rate, rather than a test at rest, and turns it into Keely Age each Monday. See Fitness.
- The skin temperature the Loop already measures. Polar makes it available through its software kit rather than in Flow; Keely uses it in Recovery.
- Every formula is public, on the methodology page.
- Your raw heart data stays on your iPhone.
Switching
The Loop keeps one Bluetooth connection. Polar reserves it for Flow; when you move to Keely, Keely has it instead. Your Flow history stays in your Polar account.
- From Polar Flow to Keely: remove the Loop in Flow, forget it in your iPhone’s Bluetooth settings, reset the band on its charger, then pair it in Keely. The step-by-step guide takes about two minutes.
- Back to Polar Flow: use Forget this Loop in Keely’s band sheet, which resets the band, forget it in your iPhone’s Bluetooth settings, then pair it in Flow.
Frequently asked questions
Can I use Keely and Polar Flow at the same time?
No. The Loop pairs with one app at a time, so you choose one. You can switch either way whenever you like.
Will I lose my Polar Flow history?
No. It stays in your Polar account and on flow.polar.com. Keely starts fresh with your Loop and learns your normal over your first nights.
How is Keely’s VO2 max different from the Polar Fitness Test?
The Fitness Test estimates it at rest, from your resting heart rate, HRV, your details and how you rate your training. Keely estimates it from effort: the pace of steady walks and runs against the heart rate they took. See Fitness.
Does Keely update the Loop’s firmware?
Yes. Keely installs firmware updates only after a successful sync, because an update erases the band.
Does Keely send data to Strava or Apple Health?
To Apple Health, yes. Connect it when you set up Keely or in Settings, and Keely saves your sleep stages, workouts with their heart rate, resting heart rate and breathing rate there. If you allow it, Keely also reads your walks and runs, with their distance, for Fitness. Not to Strava. If you rely on Flow’s other integrations, keep in mind that they only work while the Loop syncs with Flow.
Is Keely made by Polar?
No. Keely is an independent app by Metrica Fit LLC, built on Polar’s public software kit for its Bluetooth devices. It isn’t affiliated with or endorsed by Polar Electro.
Sources
- The Loop’s one Bluetooth connection, integrations and FAQ: Polar’s US store.
- Nightly Recharge: Polar support.
- Sleep Plus Stages: Polar support. SleepWise: the Loop’s manual.
- Training Load Pro: Polar support.
- Fitness Test: the Loop’s manual and Polar Fitness Test.
- Skin temperature: the Loop’s specifications and Polar’s skin temperature feature.
- Export: Export training sessions and Download all your data. Web reports: Flow web update. Trends: Polar Flow 7.37.0 (September 28, 2026).
All checked October 5, 2026. Polar and Polar Loop are trademarks of Polar Electro Oy.
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