Golden Cheetah

Overview

GoldenCheetah reads CORE data straight from your FIT file: core temperature appears on the Performance chart automatically, and skin temperature and Heat Strain Index (HSI) can be added in a few clicks.

GoldenCheetah is free, open-source training analysis software for Windows, macOS and Linux. When your watch or bike computer records CORE data, it typically writes three values into the activity's FIT file:

Before you start

You need a recent GoldenCheetah build and an activity file that actually contains CORE data.

• GoldenCheetah (latest stable release). Download it from goldencheetah.org. Older versions have weaker CORE support. Linux users should use the AppImage rather than a distro package, which is often outdated.
• A FIT file recorded with CORE paired. Most Garmin, Wahoo, COROS and other compatible devices write CORE data to the FIT file when the sensor is paired, or when the CORE Connect IQ data field is running on Garmin.
• The original FIT file. Files exported from some platforms (for example as GPX or TCX) drop developer fields, so skin temperature and HSI will be missing. Export or download the original FIT wherever possible.

Import your activity

Import the FIT file as you would any other activity; no special settings are needed for CORE data.

1. In GoldenCheetah, go to Activity → Import from file (or drag the FIT file onto the GoldenCheetah window).
2. Select your FIT file and click Import, then Save.
3. Open the activity in the Activities view.

If you sync activities from Garmin Connect or another cloud service, check that the downloaded file is a FIT file with developer data intact. When in doubt, download the original FIT from your device or Garmin Connect and import it manually.

View core temperature

Core temperature from your CORE sensor appears on the Performance chart as Core Temperature, alongside power, heart rate and speed.

1. With the activity open, select the Performance tab.
2. If Core Temperature isn't shown, open the chart settings (the menu at the top left of the chart) and tick Core Temperature in the list of series to show.

Check skin temperature and HSI in Raw Data

Skin temperature and Heat Strain Index are imported as developer data (XDATA), which you can see in the Raw Data editor.

1. With the activity open, select the Data tab, then Raw Data.
2. At the bottom of the editor, click the DEVELOPER tab (next to Basic Data).
3. Look for the skin_temperature and heat_strain_index columns.

Note the exact tab name (here DEVELOPER) and column names. You will need them in the next step. If your file uses a different tab name, click XData in the editor toolbar to list every XDATA group and series in the activity.

Plot skin temperature and HSI on the Performance chart

If skin temperature and HSI don't appear on the Performance chart automatically, add each one as a User Data series that reads the developer data with a short formula.

1. Select the Performance tab and open the chart settings (the menu at the top left of the chart).
2. Go to the User Data tab and click + to add a series.

3. Enter a name (for example Skin Temp), units (°C) and a colour, then enter this formula:

   XDATA("DEVELOPER", "skin_temperature", interpolate)

4. Click + again to add a second series named Heat Strain Index with this formula:

   XDATA("DEVELOPER", "heat_strain_index", interpolate)

5. Apply the settings. Each series appears as its own panel with its own axis, so HSI (0–10) and skin temperature (around 30–37 °C) are both readable.

The settings are saved with the chart, so the new panels appear for every activity with CORE data. Activities without these fields show an empty panel.

The first two parts of the formula must match the Raw Data view exactly, including upper and lower case: the XDATA tab name (DEVELOPER) and the column name.

Troubleshooting