Rethinking the Resonance Frequency (RF) - Part 1: Understanding Resonance

Randomized controlled trials have demonstrated the efficacy of HRV biofeedback for diverse clinical disorders like depression, diabetes, and preeclampsia (Lehrer et al., 2020, Meehan & Shaffer, in press).

The resonance frequency (RF) training protocol has strongly influenced heart rate variability (HRV) assessment and training. Steffen and colleagues (2017) ingeniously showed that RF training produced better mood and lower systolic blood pressure than RF+1 (breathing 1-bpm faster than the RF) or control conditions.

This series of posts seeks to demystify resonance frequency assessment for clinicians and performance trainers who use heart rate variability biofeedback in their practice. This first post explains resonance, the resonance frequency, two closed loops that regulate blood pressure and heart rate, and strategies to stimulate them to increase vagal tone and HRV.

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What is the Resonance Frequency?

Resonance is an amplification process that relies on simple physics (Lehrer, 2020). An external force causes a closed-loop (negative feedback) system with a fixed delay to oscillate with greater amplitude at its inherent resonance frequency (RF). Here are four examples. First, striking one tuning fork causes the second to vibrate in unison, causing the ball to swing. Graphic © Designua/Shutterstock.com.

Second, a bell struck by a Buddhist monk for prayer time resonates after the initial strike. Graphic © Amith Nag/Shutterstock.com.

Third, visualize pushing a child on a swing. There is a single frequency that moves the child the highest. The best pushing rate is analogous to its RF (Khazan, 2020). Graphic © Billion Photos/Shutterstock.com.

Finally, overloading a wine glass with sound at its RF can cause it to shatter because it cannot withstand the vibrational energy. Graphic courtesy of MARTY33 of YouTube.

Dr. Paul Lehrer provides valuable insights about resonance in this video segment © Association for Applied Psychophysiology and Biofeedback (AAPB).

Vaschillo's Two Closed-Loop Model

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