The functional threshold button activates a special function (wizard) to determine your maximum sustained effort over a defined period of time (minimal 20 minutes; more likely one hour).
iQO2 uses that maximal sustained effort to estimate your 'Anaerobic threshold'.

Step 1: Create an appropriate view

The condition to create an appropriate view on a workout, race or time-trial is simple:

  • the athlete has to push him/herself to the limits of his/her ability for at least 20 minutes
  • the workout needs to be registrated with a power device data (cycling) or speed device data (running)

Learn more about creating a view and working with views.

Step 2: Activate the FT wizard

  1. Select a high-intensity view with a duration of at least 20 minutes.
  2. Click the Functional threshold  button.
  3. A pop-up appears.
  4. Follow the steps of the wizard and choose between 3 different methods to determine your functional threshold.

  5. Depending on duration of the view, you can apply a correction factor.


  1. Drop-off:

    The biggest drop-off in the distribution chart indicates the point where you can no longer sustain the effort, and as a result this point should be just below your threshold.

  2. Peak Power 20 min:

    Here we use the peak power over 20-minutes as a measurement of your FT, calibrate by 95%.

  3. Adapted Power:

    The adapted power method uses a mathematical formula which essenstially calculates the average power adjusted by the intensity changes of the workout.
20-minutes: FT power is calibrated by 95% of the power number on 20-minutes
21-59-minutes: You have to decide which calibration you take depending on the view duration.
60-minutes: FT power = the power number over 60-minutes. No calibration is used.

Step 3: Use the functional threshold to create new training zones

iQO2 offers you the possibility to use your Functional threshold to determine your training zones. Learn more about creating new training zones based on the study of your power device data (cycling) or speed device data (running).


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