Why Isn’t My Swim Syncing From Apple Watch to Swim.com?

The Apple Watch connects to your iPhone over a wireless protocol that you’ve probably heard of called Bluetooth, specifically over a newer protocol called Bluetooth Low Energy or BTLE for short. BTLE allows many devices to connect and transfer data, and as the name implies uses less energy than many other wireless protocols that transfer data such as WiFi and the 3G and 4G cellular connections we all use in our phones.

The upside to having a low energy wireless protocol is that it’s battery friendly. The downside is that it’s relatively slow to transfer data. When dealing with small amounts of information, like a text message, this isn’t a problem. With larger datasets, like a long swim with many intervals, lengths and all the stroke counts, times, etc. associated with each, it can become problematic.

After your swim is finished, the Swim.com app saves it onto the watch and then requests that watchOS (the operating system on your Apple Watch) delivers it to iOS (the operating system on your iPhone) over Bluetooth where it can be uploaded to the web by the Swim.com app running on your phone. iOS and watchOS (both concerned about transferring the data reliably, without interruption and without being too detrimental to battery life) decide when to transfer the data.

The data transfer process over Bluetooth is a black box to us: we send the workout file in one end (on the Apple Watch) and it comes out to the Swim.com app on the other end (on the iPhone). We’re not sure exactly which state the Apple Watch and iPhone need to be in to kick off the data transfer, but we have found some tricks that can aid a quicker and more reliable data transfer:

  • Open the Swim.com app on your iPhone and refresh the feed as soon as possible (by pulling down on your list of workouts) after you’ve finished your swim
  • Leave the Swim.com app open on the Apple Watch while you do so
  • It may take a few minutes of having both apps in the foreground for your swim to transfer, even if it has transferred immediately in the past
  • Make sure your workouts are synced from Apple Watch to iPhone between swims – try to sync before your next swim
  • Try not to update the Swim.com app or the software on your Apple Watch or iPhone if you have workouts that have yet to sync
  • If your workout still hasn’t transferred after awhile, restarting the Apple Watch or force closing the Swim.com app on the Apple Watch can sometimes kick off the transfer

Short answer: the Swim.com app relies on the Apple Watch and iPhone operating systems to transfer the data for the workouts over Bluetooth, which can take a long time.

This question brought to you by you, the users in our FAQ series.  This is the first post in the series. Additional posts will follow in the coming days. Have a question about the Swim.com app?  Ask us in the comments below or email it to support@swim.com

4 thoughts on “Why Isn’t My Swim Syncing From Apple Watch to Swim.com?

    1. Unfortunately doing that is just adding an extra, unnecessary step and it would not actually change the process of how the file transfers.

  1. Maybe a little off topic. But you upload data not only to swim.com, but also to the Apple Activity application. I can see my swims in activity app once data is imported from the watch, but unfortunately I cannot see all the information about calories burned.

    This is strange as I see that calories get accounted in my day circles (red circle). But when I move to the the list of my trainings, choose to see my swimming training I see 0 active calories burned, and 0 total calories for that training.

    Can you check if the training data is imported correctly to the activities app?

    screenshot of my swim with 0 calories – https://gyazo.com/8d907a1ccdf784904193fa90f05432af

    screenshot of how it should be – https://gyazo.com/768d4a22f9e7d9e28d2c151847737ff2

    1. Hi Egor-
      The 0 calories report on the workout summary in Activity is happening because we don’t actually support the calorie metric yet on Swim.com. Apple has the calorie metric API open to us in Activity – so it’s definitely possible to add it, and we will be investigating it for a future app update. However, there are currently issues with the HR data coming from the Apple Watch, which can affect the accuracy of calories burned while swimming. I’ll digress further below..

      You can usually get a ballpark estimate of calories burned using height, weight, age, and gender, but in order to get it within an acceptable rate of accuracy you also need to include fitness level. Heart rate data is really the only way to put a quantitative measure on fitness level (aside from V02 max, which likely isn’t coming to swim tracking devices soon). The Apple Watch is the first device we’ve supported the HR metric on, mostly because it’s one of the only devices that works in water without requiring a special swimming HR chest strap and hasn’t had WHR disabled while swimming. Because the HR data coming from the Apple Watch is not to our accuracy standards yet, we likely won’t include calorie count until it does.

      While you are getting a 0 calories burned result for the Swim.com workout in Activity, you may notice that you ARE getting calorie count in Activity’s “Move” ring, though. This is happening because Activity is adding estimated calories burned from the data it is taking from your Apple Watch and not what is sourced from Swim.com. The Apple Watch has auto-detection algorithms for swimming, so even if you do not start a native apple watch workout or a Swim.com workout and you go swimming, it will pick up these strokes and add them to your data. This happens simultaneously while recording a swim workout with the Swim.com app.

      This breakdown of sourced data is available if you open the Health app and then navigate to Activity>Swimming Distance and then tap on the graph. There you will be given a list of dates and you can further break it down on each day. Here you can see Health is pulling data sourced from Swim.com AND from Apple Watch’s auto detection algorithms at the same time. Health is taking that data sourced from the Apple Watch auto algorithms and then adding that to your calorie total (the Move ring in Activity). When you view the workout itself though (sourced from Swim.com) on Activity, you’ll get a 0 calorie because we’re not writing that data.

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