Fitbit Air Lost My data – I Want It Back.

Finding Fitbit – A tale of an open water swimmer’s epic journey to find a lost heart rate recording.

This is ridiculous. When you press stop on your Garmin Fenix, it’s annoying that you have to wait 10 seconds or so to see the summary. Really annoying when you might have a $500 or $1,000 watch running at glacial speed. But you do eventually get the summary, and Garmin does a pretty good job showing you lots of post-workout summaries on your watch.

Fitbit Air is obviously far cheaper than any Garmin; however, I’ve been waiting 10 to 30 minutes for it to sync my workout to the Google Health app. For me, that is completely unacceptable.

After a swim test today, I was pretty furious that no swim data appeared. The swim was under half an hour, but the whole test took me over three hours, including travel. Every other device worked. But Fitbit decided not to show me anything.

So, like on previous occasions, I tried to assign a workout to a specific time period. ‘Swim’ would seem a reasonable choice considering I’d just swum. I waited a while, but unlike before, nothing surfaced after an hour. I then went back to the built-in Gemini AI tool. I’ve been using this more for troubleshooting than getting insights. It’s great and helpful for troubleshooting, but I would rather there were no troubles to deal with in the first place. This is becoming ridiculous.

Further, it seems that my workaround of assigning a workout to a time span doesn’t work if you assign it as a swim. The AI told me this and then advised me to delete the manual entry, which I started to do. However, as you can see from the screenshots, this then said, “I am going to delete your data!” I don’t believe it will actually do that; rather, it will delete the exercise period I overlaid on the raw data. But I’m not sure. As a precaution, I changed the swim’s time period to an imaginary one earlier in the day.

Next, the AI came up with some nonsense that no data was recorded. It was a swim, and the Air was protecting itself, or so the AI said. It was stoppig the chance of getting bad data due to water ingress between my skin and the Air. This is complete nonsense, as it had no idea it was swimming when it recorded the data. I classified it as swim after the workout was complete!

There was no way of getting the data in Google Health, it told me. It then told me to look at the raw data on Fitbit.com (retired in 2024) and at Takeout.google.com. I think I know what that latter one is, and I’m not going there to waste three more hours of my life.

Having hoped I had run out of things to complain about, I was wrong, as the data was pants. Or, if you prefer the correct statistical interpretation for Swim HR data, it was…fair.

Open Water Swim Accuracy Results

Fitbit Air, like other devices, is prone to flipping while swimming, and to water entering the gap between the skin and the sensor. To mitigate those variables, I put it under my wetsuit sleeve as I did with the Amazfit Helio Strap on the other wrist. If you do this and have two spare biceps, the only obvious next step is to wear a Polar SENSE HR strap and a Whoop MG. I have two biceps. I did that. I also have a chest, which seemed the natural place to put my Fourth Frontier ZONE ECG chest strap. This is a personal record – 5 heart rate monitors, all placed sensibly.

DCRainmaker’s Analyzer tool produced some stats which would normally be summarised for swimming as

Fitbit Air accuracy: Fair to Poor for open water swimming.

• It underestimates HR by ~10.5 bpm vs Polar SENSE (Fair) and ~18.5 bpm vs Amazfit (Poor), while Polar and Frontier align closely.

Fitbit Air vs Frontier ZONE (reference):

• Bias: -10.9 bpm (underestimates)
• LoA: -21.7 to +41.7 bpm (wide range, ~18-34% relative at avg HR)

When all devices fail to agree, you need to understand what is happening during the sport. Even my trusty Polar SENSE could be susceptible to error when on the arm during swimming. Apart from the dropout at 18:00, it is a good track, but the Frontier ZONE chest strap should be taken as the reference device due to its position on the chest and general reliability as an ECG chest strap.

You don’t need stats when you can see with your eyes that the Fitbit Air data is rubbish. It catches up with reality at 28:00 and performs Ok after that.

One further anomaly is the Helio Strap data. You can see it is oddly shown above with an average of 91.81 bpm. This is because there were frequent dropouts due to arm movement. If I show the dropouts (zeros), you get the following – remarkably similar to a graph I earlier showed with Fitbit Air on a treadmill. Such dropouts are caused by motion artifcts.

Take Out

The simple takeaway is that you have to manually record your Fitbit Air swims as runs.

FAQ

Q: Does Fitbit Air track swimming?

A: It records raw data during swims but manual workout assignment as swim type is unreliable. Record as a run instead.

Q: How do I recover lost Fitbit Air swim data?

A: Assign the time period manually in Google Health and select Run rather than Swim. The raw HR data is captured; the swim classification causes the sync issue.

Q: Is Fitbit Air accurate for open water swimming?

A: Fair to Poor. In testing it underestimated HR by approximately 11 bpm against an ECG chest strap reference, with wide limits of agreement.

Last Updated on 30 May 2026 by the5krunner

the5krunner

tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors. ID