Include HR and Power zones into the fit file

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Florian Muehl

• January 13, 2026 12:43

Please include custom hr and power zones into the fit files. Other training platforms can use this data.
Suunto for example needs this to calculate your time in hr zones correctly.

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  Aishwarya

  • February 23, 2026 12:31

  Hi Florian, Thanks for bringing this up.
   
  Karoo records the heart rate and power data in the FIT file. However, Karoo does not currently write the HR or power zone data into the FIT file in a way that external platforms can directly access.
   
  Suunto recalculates and interprets zone metrics within its own ecosystem and algorithms. For imported activities to reflect time in zones exactly as in native Suunto recordings, Suunto would need to process and calculate those values on its end. Using the same zone settings and values for HR and power on Karoo and Suunto may increase the odds of consistency between the platforms, but you may still see some discrepancy based on the individual logic Suunto uses to compute the zones.
   
  We are sorry that we do not have a dedicated timeline to share with you on writing the zone data to the FIT file.

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  Johan Ulijn

  • March 19, 2026 21:35

  Please put this with higher priority on the timeline. A lot of Suunto users (who moved away from Garmin and decided to use Hammerhead instead) are waiting for this. And since there is some kind of partnership between Suunto and Hammerhead (according their websites), we may expect that we could see useful power zone data in our Suunto app. Currently we see only power graphs but not the time in the powerzones zones. I guess some from Hammerhead should work with Suunto to solve this issue togather.

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