A wrist worn heart rate monitor includes a photoplethysmogram (PPG) sensor and an inertial sensor. Signals from the inertial sensor are used to identify and remove noise from the PPG signals. An initial heart rate value is selected from a number of heart rate candidates that remain in the resulting PPG spectrum and is used to track the heart rate of the user. The PPG spectrum is monitored while tracking the heart rate to determine if the selected initial heart rate value is in error. The PPG spectrum may be monitored by determining a correlation of possible heart rate candidates in each PPG spectrum to the previous heart rate candidates and resetting the heart rate value accordingly. Additionally or alternatively, the PPG spectrum may be monitored by determining when only a single heart rate candidate is present in consecutive PPG spectra and resetting the heart rate value accordingly.
