Getting Your FTP Estimate
Before you can get your functional threshold power (FTP) estimate, you must pair a power meter with your watch (Pairing Your Wireless Sensors), and you must get your VO2 max. estimate (Getting Your VO2 Max. Estimate for Cycling).
The watch uses your user profile information from the initial setup and your VO2 max. estimate to estimate your FTP. The watch will automatically detect your FTP during steady, high intensity rides with a power meter. For best results, you should also ride with a heart rate monitor.
Parent Topic: Performance Measurements