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 firstname.lastname@example.org