Cycling workout targets: power or heart rate

IntervalCoach can prescribe your rides by power or heart rate. You pick which one under Settings → Training → Cycling Workout Targets. Power is the default.

What each mode needs in Intervals.icu

• Power-based (default) needs an FTP, so a power meter or smart trainer. Targets are written as a percentage of FTP, for example "88-93%". Which FTP value gets used is your choice: see FTP: Manual vs Estimated (eFTP).
• Heart rate-based needs your LTHR or max HR set in your Intervals.icu profile. Targets are written as heart-rate zones, for example "Z2 HR". Best for outdoor riding without a power meter. Set the threshold before you switch: the zone targets have nothing to resolve against without it.

What changes when you choose heart rate

Two things are worth knowing before you switch.

Your workouts arrive as zones rather than watts, so there are no power targets in the file. A smart trainer has nothing to hold in ERG mode. Heart-rate mode is built for riding outdoors by feel, not for the turbo.

Very short efforts, under about half a minute, come through as free-ride steps instead of a zone. Heart rate lags too far behind to steer a 20-second sprint, so the instruction is the effort itself rather than a number to chase.

Which should I pick?

If you ride with a power meter or a smart trainer, stay on power. It is immediate, it does not drift, and it is what the training load is built on.

If you ride outdoors without a meter, choose heart rate. It responds to heat, fatigue and altitude in a way power does not, at the cost of lagging on anything short.

My targets look empty or wrong

This almost always means the threshold for your chosen mode is not set in Intervals.icu.

Set the matching value there: FTP for power mode, LTHR or max HR for heart rate. Or switch to the target you already have configured, under Settings → Training → Cycling Workout Targets.