Instantaneous heart rate, last 60 seconds.
You'll breathe at four paced rates — 5.5, 5.0, 4.5 and 4.0 breaths per minute — for one minute each, resting between them. Whichever rate makes your heart rate swing the most is your resonance frequency: the rate at which breathing and the baroreflex fall into phase.
Sit upright and still, breathe into your belly, and follow the capybara — she grows as you breathe in and shrinks as you breathe out. The exhale is deliberately longer. Don't strain for depth; smooth and comfortable beats big.
The test finds your rate; this is the practice — breathing at it, twenty minutes or so a day. No strap needed. A recording started on the Monitor tab keeps running while you breathe here, so start one first if you want the session on the record.
One column per test, oldest on the left. A row that stays lit means your resonance frequency is stable; wandering marks mean it moves — which is the thing worth knowing. Remember that neighbouring rates separate weakly, so treat a one-step move as soft.