How to add heart rate from your watch to a bike computer ride

You rode with a bike computer on the bars and a watch on your wrist. The bike computer has the route, speed, and power. The heart rate is on the watch, because the strap was paired to the watch, or because the watch measured it at the wrist and the bike computer never saw it. Now there are two activities of the same ride and neither one is complete. You can combine the two files into one activity that has everything.

Get both files

From the devices. Plug each one in and look in the activity folder. On a Garmin it is Garmin/Activity, with the files named by date and time.

From Garmin Connect. Open each activity, click the gear icon, and choose Export Original. You get a zip with the .fit file inside. The editor opens the zip as it is.

From Strava. Open the activity, click the three-dot menu, and choose Export Original.

Combine them

1. Open the bike computer's file in FIT File Editor. Open this one first: the activity keeps its sport, device, laps, and start and end times.
2. Press the plus button and add the watch's file.
3. A notice says what was added, for example "Added heart rate from" and the file name. The heart rate now shows on the timeline under the ride.
4. Press Export. You get one .fit file with the bike computer's ride and the watch's heart rate.

The editor fills in only what the first file is missing. If the bike computer recorded no heart rate, it takes the watch's; anything the bike computer did record, like power, speed, or GPS, stays as it was. Heart rate, power, cadence, GPS, elevation, temperature, and speed can all be filled in this way. See combine two devices for the details.

Upload it

Delete both originals first, the bike computer's and the watch's, on every site they synced to. Then upload the combined file. If either original is still there, the upload can be refused as a duplicate; the duplicate activity guide covers the order that works.

Worth knowing

• Open the full-length one first. Heart rate is added only for the time both devices were recording. If you started the watch late or stopped it early, that stretch of the ride has no heart rate, and the ride itself is unchanged.
• The other way round works too. If you'd rather keep the watch's activity, open the watch file first and add the bike computer's file. The watch file then picks up power, cadence, or GPS it didn't have, and keeps its own sport and device.
• "Adds nothing new". If the editor says the second file adds nothing new, both files already have the same kinds of data, or you added the same file twice.
• A ride split in two is a different fix. Two recordings one after the other, like a watch that died and was restarted, get joined end to end. See Garmin died mid-ride.