LF Peak, HF Peak, Coherence & Resonance Breathing

Power tells you how much: the peak tells you where

If you’ve read about the frequency-domain bands, you know HRV can be split into slow, medium and fast rhythms, and that each band holds a certain amount of power. Power is a magnitude: how much of your heart-rate variability lives in that band. But every band also has a peak: the single frequency inside it where the energy piles up highest. Power is how much; the peak is where. They are two different questions about the same spectrum, and the peak turns out to be the one you can steer with your breath.

Think of it like a radio dial. The total loudness is the power. The exact station the needle lands on is the peak. Two readings can be equally “loud” while their needles sit in completely different places, and where the needle sits tells you which control system is doing the driving.

The HF peak sits at your breath

Every time you breathe in, your heart speeds up a little; every time you breathe out, it slows. This is respiratory sinus arrhythmia, and it’s the single largest, cleanest source of fast HRV. Because it is driven directly by breathing, the HF peak lands exactly at your breathing rate. Breathe fifteen times a minute and the peak sits at 0.25 Hz (15 ÷ 60). Breathe six times a minute and it drops to 0.1 Hz.

That makes the HF peak a kind of honesty check on the reading. If you meant to breathe slowly but the peak shows up high and fast, the reading knows you were breathing quickly. The RMSSD and pNN50 vagal-tone metrics move with this same respiratory rhythm, which is why slow, even breathing lifts them too.

The LF peak and the baroreflex

The LF peak sits lower, right around 0.1 Hz, and it comes from a different machine entirely: the baroreflex, the feedback loop that keeps your blood pressure steady. When pressure drifts up, the loop slows the heart; when it drifts down, it speeds up. That correction loop takes about ten seconds to go around, which is why it oscillates near 0.1 Hz: one cycle every ten seconds.

Here’s the elegant part. Your breathing rhythm and your baroreflex rhythm are two separate oscillators, but they can be brought into step. If you slow your breathing down until it also cycles near 0.1 Hz, the two rhythms stop competing and start reinforcing each other. That alignment is the whole idea behind resonance-frequency breathing.

Resonance: pushing the swing at the right moment

Every system that oscillates has a resonance frequency: the one pace at which a small, well-timed push produces the biggest swing. Push a playground swing at random and it barely moves; push it at its natural rhythm and it flies. Your cardiovascular system behaves the same way. As Lehrer and Gevirtz (2014) describe, breathing at your personal resonance frequency (for most adults near 0.1 Hz, about six breaths a minute) makes the breathing rhythm and the baroreflex rhythm resonate, and beat-to-beat variability swells to its maximum.

When that happens, the messy, spread-out spectrum collapses into one tall, narrow peak near 0.1 Hz. That concentration of power into a single clean rhythm is what’s meant by coherence. A highly coherent reading looks orderly (a smooth, regular wave instead of static) and it’s the fingerprint of a nervous system settling into a calm, rhythmic state.

Convert any breathing pace to its frequency and see whether it lands in the resonance zone:

The app’s paced-breathing styles

Autonomic offers several guided breathing patterns, each with an inhale and exhale count in seconds. The sum of the two counts sets your breathing period, and that period fixes where the HF peak lands. Slower patterns pull the peak down toward the 0.1 Hz resonance zone:

Notice how the longer patterns march the target peak downward. The 4 / 6 and 5 / 5 styles sit closest to resonance, which is why they tend to produce the tallest, sharpest peaks and the highest coherence. If you’re new to slow breathing, starting at 4 / 4 and working down over a few weeks is gentler than jumping straight to the slowest pace.

Grading the peaks

For an unstructured resting reading, Autonomic grades where each peak lands. The bands are non-linear, both too-low and too-high can pull a peak out of its healthy zone, so they read most clearly as a table rather than a left-to-right bar.

LF peak (Hz): you want this parked near the 0.1 Hz baroreflex frequency:

HF peak (Hz): this tracks your breathing rate, so a comfortable resting breath keeps it in range:

A very low HF peak often just means you were breathing slowly (which is fine, and even the goal during a paced session), while a very high one can mean rapid, shallow breathing. This is why the app scores paced and unstructured readings with different expectations, a distinction covered in the autonomic score and grade bands. For the underlying methods, the Kubios HRV analysis reference and the 1996 Task Force standards both detail how these peaks are located.

Slow breathing at resonance isn’t only a way to score well on a reading: it’s a trainable skill. Practiced regularly, it becomes one of the most reliable tools for calming an over-revved nervous system, which is why it features so heavily in recovery from post-viral dysautonomia. And because it acts directly on the autonomic nervous system, a few minutes of it is one of the few things you can do to shift your state on demand.

The bottom line

The LF and HF peaks answer where your heart-rate rhythm concentrates, not how much power it holds. The HF peak sits at your breathing rate; the LF peak sits near 0.1 Hz, in the baroreflex band. Breathe slowly enough, around six breaths a minute, and the two rhythms resonate, driving a single tall, sharp peak and high coherence. That’s the state the app’s paced-breathing styles are built to reach, and it’s the most direct lever you have for raising HRV in the moment. Track where your peaks land, practice the pace that feels effortless, and let the trend show you the skill taking hold.