By PulsHealth. Updated
Research reviewed .
What is FTP in Apple Health?
Functional threshold power, or FTP, estimates the maximum average power sustainable for 60 minutes of cycling. It uses watts, like cycling power, but describes an estimated capacity rather than output at every moment of a ride.
| Item | How to read it |
|---|---|
| An FTP sample | An estimate recorded at a particular time |
| A power sample | Output during a riding interval |
| Power zones | Intensity bands configured using an FTP reference |
| A gap between FTP samples | No new recorded estimate; not zero capacity |
Is an FTP value proof of a one-hour test?
No. Apple documents automatic estimated FTP samples during cycling workouts. The support guide also allows a custom FTP for power-zone settings. Neither the type's name nor an estimate establishes that a rider completed a laboratory test or a maximal one-hour effort. A configured zone reference and an exported HealthKit sample should not be assumed to be the same stored object.
Why might an estimate update irregularly?
FTP is not a continuous sensor stream. Compare intervals between estimates and changes in the values, along with the rides and equipment supporting them. Apple describes compatible cycling accessories and requires date of birth, height and weight for power-zone calculations. Recording an ordinary cycling workout does not guarantee a new FTP estimate.
What did the example-data investigation find?
The selected October 2025–September 2026 database window contained no FTP samples, FTP workout-series values or FTP aggregates. Update cadence, change size and relationships with ride power or body mass could not be measured. Cycling distance existed, but distance alone cannot estimate sustainable power, so no empirical FTP chart or reference range is presented.
How can FTP be compared fairly?
Use repeated estimates with comparable devices and methods, and retain the date of each estimate. A change may reflect training, measurement conditions or a different estimation method. There is no universal healthy watt threshold here. Comparing watts per kilogram requires a temporally appropriate weight; dividing by an unrelated weigh-in can create a misleading result.
How does FTP relate to power zones?
Apple's watch settings can calculate power-zone boundaries from an FTP value and allow customization. Check the actual configured zones rather than assuming a fixed number of bands or percentages. For historical analysis, preserve the reference available for each ride instead of applying today's settings retrospectively.
Understanding your records
Recording frequency, source and coverage affect what you can conclude from this data. Read the recording guide.