I have a Garmin Forerunner FR220. When plugged into a Windows 7 computer by the USB device, it shows up as a USB Mass Storage Device, initializing a "Garmin FR620 Flash USB Device", and connects as FAT formatted Flash storage.
Seeing 620 does cause me a bit of annoyance, as I know that my 220, which lacks a number of features of the 620, watch is physically identical just with the speed inhibitor turned off [1]. Makes me miss my TI 430 Chronos, but that didn't have GPS. The FR225 is the first version with the optical heart rate monitor, but I believe it and the current FR235 will behave similarly.
All the activity data is stored on the mass storage device in .FIT files. Here's an example file [2] which you can compare to my Strava upload at [3]. Use the tools at [4] to convert and edit it into GPX format, and the schema at [5] to tease out pedometer/heart rate data from this XML text. You'll probably end up using GPSBabel [6] to analyze it.
Garmin is probably the most common activity tracker for actually running, biking and so on. For just sleep tracking and resting heart rate tracking, or daily step counters, Fitbits that lack GPS are much more popular. But they don't allow manual export of data [7]:
> Welcome to the Fitbit Family @JohnDiver! The stored data on your Fitbit Flex can be taken out only via Bluetooth with an internet connection. It can be synchronized with a computer or with a supported mobile device. Your tracker stores at least 7 days of detailed minute-by-minute data. Summary data (calories, distance, and steps) will be stored for 30 days. If you are experiencing syncing issues, please take a look at the basic troubleshooting steps.
> If the above doesn't help you please let us know what type of difficulties are you having to transfer your data to your Dashboard? Looking forward to your new comments!
The new Garmins do have activity tracking features; I'd be interested to see if their data can be accessed as easily as the .FIT activity files.
[1]: https://www.joelonsoftware.com/2004/12/15/camels-and-rubber-...
[2]: https://drive.google.com/file/d/1H6sBu3XaQgUyTyAhO1Oz7jKL0hx...
[3]: https://www.strava.com/activities/1287343609
[4]: https://www.dcrainmaker.com/tools
[5]: https://www8.garmin.com/xmlschemas/TrackPointExtensionv2.xsd
[6]: https://www.gpsbabel.org/
[7]: https://community.fitbit.com/t5/Flex/Retrieve-raw-data-from-...