Embodiments are directed to methods and systems for adaptive heart rate monitoring. In one scenario, a method for adaptive heart rate monitoring includes receiving, from a pulse-oximeter, a sensor signal, where the sensor signal is photoplethysmogram waveform. The method next includes generating a frequency-domain photoplethysmogram waveform by applying a transform algorithm to the sensor signal, and dividing the resulting frequency-domain photoplethysmogram waveform into discrete frequency regions. The method further includes identifying a fundamental heart rate harmonic within one of the discrete frequency regions by analyzing each discrete frequency region according to a specified analytic algorithm, and triggering a user interface to display a biometric measurement corresponding to the identification of the fundamental heart rate harmonic.
