Low-Frequency Power and Coherence Index HRV Biofeedback Training Success
The low-frequency (LF) band (0.04-0.15 Hz) is affected by breathing from ~3-9 bpm (Task Force, 1996). The baroreflex system’s resonance falls within the LF band. The baroreflex regulates blood pressure and heart rate. Graphic © Alila Medical Media/Shutterstock.com.
Caption: (1) baroceptors detect blood pressure changes and send signals to the medulla via the glossopharyngeal nerve; (2) the NTS increases the firing rate of the vagus nerve to slow the heart; (3) heart rate slows.
While researchers disagree about the sources of activity within this band, a sympathetic role during resting measurements appears unlikely (Hayano & Yuda, 2019). LF power may be produced by the PNS and blood pressure regulation via baroreceptors (Akselrod et al., 1981; Berntson, Quigley, & Lozano, 2007; Lehrer, 2021; Task Force, 1996) or by baroreflex activity alone (Goldstein et al., 2011). Use LF-band power to assess the success of heart rate variability biofeedback (HRVB) while your client is breathing from 4.5-7.5 bpm (Shaffer & Ginsberg, 2017). Dr. Inna Khazan generously provided these spectral plots of LF power (shown in green) across the pre-training baseline, HRV biofeedback training, and post-training baseline.
Caption: The client is breathing at normal rates (15 and 14 bpm) during both baselines, compared with slow-paced breathing (6 bpm) during HRV biofeedback training. We should only expect increased LF power during HRV biofeedback training. A single high amplitude peak near 0.1 Hz signals high coherence within the HeartMath Institute model. Graphic © HeartMath Institute.
Caption: This display shows instantaneous heart rate at the top. Bottom left is an HRV spectral display. Note that there are two peaks around 0.1 Hz instead of one. Bottom right are coherence ratios. Note that the individual has only achieved 68% high coherence at the low challenge level.
Coherence is a proprietary HeartMath term that means a "narrow, high-amplitude, easily visualized peak" from 0.09-0.14 Hz (Ginsberg, Berry, & Power, 2010, p. 54). When clients achieve high coherence when experiencing feelings of appreciation and slow-paced breathing, the heart rate waveform shows large, regular oscillations (respiratory sinus arrhythmia) that resemble ocean waves. Summary The low-frequency (LF) band extends from 0.04-0.15 Hz. LF power may be produced by the PNS and blood pressure regulation via baroreceptors or by baroreflex activity alone. However, a sympathetic contribution during resting measurements is unlikely. Use LF-band power to assess the success of heart rate variability biofeedback (HRVB) while your client is breathing from 4.5-7.5 bpm. When clients achieve high coherence when experiencing feelings of appreciation and slow-paced breathing, the heart rate waveform shows large, regular oscillations (respiratory sinus arrhythmia) that resemble ocean waves. Learn More
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