1/f fluctuation in forests may help explain a feeling you already know: you step beneath the canopy and your shoulders drop — you hadn't noticed they were raised. Most people assume this is simply a nice walk. But what if it is something far more precise than that?
What your body already knows
Shinrin-yoku has been studied for decades by researchers across Japan and beyond. Time spent in forest environments produces measurable reductions in cortisol, blood pressure, heart rate and self-reported anxiety. These are not anecdotal impressions. They are data.
But why? What is it about a forest specifically that produces this response? The answer, it turns out, involves physics.
At the Manza Nature Information Centre (万座しぜん情報館) in Gunma Prefecture, we came across an exhibition dedicated to exactly this question, titled "The Healing Effect Brought by 1/f Fluctuation." What it explained changed how we understand what happens to our guests on every walk we lead.
The hidden rhythm of the natural world
In physics there is a phenomenon called 1/f fluctuation — known in Japanese as yuragi (ゆらぎ), a gentle wavering. It describes a specific relationship in wave patterns: one that sits precisely between pure order and pure randomness.
Think of it this way. A metronome is perfectly regular, and after a while it becomes numbing. White noise is completely random, and it quickly becomes exhausting. 1/f fluctuation is neither. It is the sweet spot: regular enough to feel safe, varied enough to stay alive — and the human nervous system appears deeply attuned to it.
The forest is speaking a language that our bodies already know.
Where does this pattern appear? Almost everywhere in nature. The filtering of light through leaves — komorebi (木漏れ日) — follows a 1/f pattern. So does the sound of a mountain stream: measurements at the Manza River found a value of 0.987, almost perfectly matching the ideal. Birdsong follows it. The ripple of a pond follows it. Even the growth rings of a tree carry the signature.
And it appears within us too. Our heartbeat intervals, our eye movements, our neural firing patterns all follow the same gentle, irregular-yet-patterned rhythm.
What this does to your brain and body
When the body perceives 1/f fluctuation through the senses, a cascade of responses may follow. According to the research of the Japanese physicist Toshimitsu Musha, one key mechanism is the stimulation of alpha waves in the brain — the state of relaxed alertness that most of us find very difficult to reach on an ordinary working day. Alpha waves are the brain's way of saying: I am safe, I am present, I can rest.
Alongside this, exposure to natural 1/f environments is thought to help regulate the autonomic nervous system, which governs heart rate, breathing, digestion and our stress response. When it finds balance, the physical sensations are unmistakable: deeper breathing, slower pulse, a groundedness that is difficult to explain but impossible to miss.
This is not mystical. It is physiology.
And importantly: 1/f fluctuation is only one part of the experience. A real forest also means fresh air, movement over natural terrain, release from digital demands, quiet company, and all five senses engaged at once. The science can enrich our understanding without reducing the experience to one mechanism.
The forest is doing more than you realise
Through your eyes: the shifting patterns of komorebi, the swaying of trees, the ripple of water — all of it visual 1/f fluctuation, registered by your nervous system as calming and alive.
Through your ears: birdsong, stream water, wind through leaves. The acoustic environment of a healthy Japanese mountain forest is extraordinarily rich in 1/f patterns, in a way a city park or a nature video simply cannot replicate.
Through your skin: bark under your fingers, uneven ground underfoot, the temperature shifting between sunlight and deep shade.
Through your nose: phytoncides, the aromatic compounds released by trees. Their concentration changes with tree species, season and weather, so each forest has its own scent.
What this means for you
We want to ask you something honestly. When did you last feel genuinely rested? Not merely physically rested — mind-rested. The kind of quiet that comes not from switching off, but from being completely, peaceably present somewhere.
For many of our guests the answer surprises them. It has been months. Sometimes longer. The demands of modern life can accumulate, and most of us learn to carry that weight so routinely that we no longer notice it.
A guided forest bathing walk does something different. It does not ask you to stop thinking, or to meditate, or to achieve any particular state. It simply places you, slowly and intentionally, within an environment your nervous system was designed to respond to — and then it gives you time.
Time to let your breathing find its own pace. Time to stand beside a stream and listen to a sound that measures almost perfectly as 1/f — and let your body remember what calm actually feels like.
Walk with us in Hakone
Guided shinrin-yoku sessions in cedar and hinoki forest, within easy reach of Tokyo. No rushing, no performance, no destination to reach.
Book a sessionScientific content on 1/f fluctuation is drawn from the exhibition "The Healing Effect Brought by 1/f Fluctuation" at Manza Shizen Johokan (万座しぜん情報館), Gunma Prefecture, referencing the work of physicist Toshimitsu Musha. This post does not constitute medical advice.