top of page

Rethinking the Resonance Frequency (RF) - Part 2: Slow-Paced Breathing

Updated: Mar 24


woman meditating


Resonance frequency (RF) assessment identifies the stimulation frequency producing the greatest amplitude heart rate oscillations in one to two sessions. We can assess the RF using slow-paced breathing (SPB) or slow-paced contraction (SPC) methods. This installment focuses on the slow-paced breathing method. We will discuss the equipment used in RF assessment and the importance of breathing assessment and training. Although we recommend using a respirometer, this does not mean you cannot measure the RF or provide effective heart rate variability (HRV) training without one. Instead, we believe that a respirometer offers assessment and training advantages.


In the third installment, we will cover RF assessment using slow-paced contraction. In the final installment, we will describe stepped and sliding protocols and their RF selection criteria. We will suggest ways to simplify RF assessment.


Click on our narrator icon to listen to this post.






Watch Dr. Inna Khazan's Heart Rate Variability: Harnessing Your Own Personal Superpower




Equipment for RF Assessment Using Slow-Paced Breathing


For publishable research, you will need an electrocardiogram (ECG) with a respirometer. We encourage using an ECG or PPG sensor with a respirometer for clinical work. Smartphone apps like Optimal HRV offer automated RF assessment using a compatible PPG sensor and their proprietary pacing display for personal training.



ECG or PPG?


Clinicians use the PPG and ECG to monitor heart rate (HR) and heart rate variability (HRV). A PPG sensor detects the pulse wave as it travels through the vascular tree.


NeXus BVP sensor


Graphic © paulista/ Shutterstock.com.

Red blood cells

ECG sensors detect the R-spike of the QRS complex, measuring the time between successive heartbeats. A wrist placement trades ease of application for vulnerability to movement.


ECG wrist placement


Graphic © arka38/Shutterstock.com.

R-spike of ECG