The gap between beats,
not the beats.
A healthy heart is not a metronome. The interval between one beat and the next is always shifting, and the size of that shift is heart rate variability.
It works because your two autonomic branches act on different timescales. The vagus nerve releases acetylcholine and acts in under a second, so it can change the length of a single interval. The sympathetic side works through a slower chemical cascade and takes several seconds, so it cannot.
That difference is the whole measurement. The fast, beat-to-beat movement is a read of vagal activity, which is the branch that handles recovery, digestion and sleep.
We report RMSSD, the standard index of that fast vagal component, and we track your overnight average rather than a single reading.
A chest-worn single-lead ECG sensor logging every R-R interval at millisecond resolution, continuously, for 72 hours. You wear it through work, training, dinners and sleep.
A one-minute phone reading cannot produce a valid frequency measure, and one mis-detected beat distorts the result. Of 28 studies on very short readings, only 3 used an adequate agreement test.
Where recovery actually occurred across three days and nights, what your body reacted to and when, how alcohol and late meals changed your night, and an estimated fitness category.
Five things the data
reliably shows.
One drink is not nothing
In 4,098 working adults measured on their own drinking and non-drinking nights, a recovery index across the first three hours of sleep fell 9.3 points at low intake, 24.0 at moderate and 39.2 at high. Every result significant, including the low dose.
Being fit does not protect you
In the same cohort the effect was similar in physically active and sedentary people, and stronger in younger ones. Training hard does not buy back the night. This is the finding clients argue with most and the one the data is clearest on.
A weekend lie-in does not clear the debt
After repeated weeks of halved sleep, autonomic recovery needed at least three nights to restore, with vagal activity overshooting baseline on the second night as the debt was repaid.
Training moves it, and the effect is large
Across 16 randomised trials in 623 adults, exercise training raised RMSSD with a standardised effect of 0.84. For a measure this noisy between people, that is a big within-person shift.
The vagal metrics fall before 60
Across 260 people aged 10 to 99, RMSSD had fallen to 47 per cent of its young-adult value by the sixth decade, then levelled off. Which is exactly why your own trend matters more after 40, not less.
Slow breathing works, and it outlasts the session
A synthesis of 223 studies found vagal activity rose during slow breathing, immediately after a single session, and after a multi-week program. The last two matter most, because they are not just the mechanics of breathing slowly.
The limits are
the honest part.
Most of this industry presents HRV as a single score you can compare with other people. That is the one thing it cannot do.
Across 44 studies and 21,438 healthy adults, the variation between individuals ran to several orders of magnitude. Two healthy people of the same age and sex can differ tenfold. Your number against someone else's means almost nothing. Your number against your own last month means a great deal.
HRV is a non-specific measure of autonomic state. It does not identify, confirm or rule out any condition. Anything clinical goes to a doctor, and for our clients that is Orba Health.
It detects physiological activation. It cannot tell a difficult meeting from a double espresso, a hot room or the stairs. Your diary supplies the cause, the sensor supplies the timing.
In trained athletes fitness can improve while HRV falls. Unusually high variability can also reflect an irregular rhythm rather than good recovery. Direction without context is not information.
The VO2max figure from this method has been shown to diverge from laboratory measurement by around 19 per cent. We report it as a category, never as a test result. If you want the real number, we test it.
Posture, breathing rate, time of day, caffeine and last night's training all move the number. Readings taken differently cannot be compared, which is why we run a fixed protocol.
Three days, then a
conversation that changes something.
Fit the sensor
Ten minutes in the studio. You leave wearing it and carry on with an ordinary week, including the parts you would rather not record.
Three days and nights
Work, training, travel, dinners, sleep. You log what you were doing so the physiology has context, which is the part most people skip and the part that makes it useful.
We read it together
Not a report emailed to you. We sit down and go through where recovery happened, where it did not, and which two or three things in your week are doing the damage.
Change something and retest
One or two changes, not twenty. Then we measure again under the same conditions, so the comparison is real and you can see whether it worked.
HRV sits inside coaching rather than beside it. The training week, the sleep and the alcohol conversation all move the same number, and all three are things your coach is already working on.
Heart rate variability,
answered.
What is HRV analysis?
Heart rate variability is the shifting gap between one heartbeat and the next. We report RMSSD, the standard index of the fast vagal component, and track your overnight average rather than a single reading.
How does the 3 day test work?
You wear a chest-worn single-lead ECG sensor for 72 hours, through work, training, dinners and sleep. We fit it in about ten minutes in the studio. You log what you were doing, and we sit down and read the results together.
Why 72 hours and not a one minute reading?
A one-minute phone reading cannot produce a valid frequency measure, and one mis-detected beat distorts the result. Three days and nights show where recovery actually happened and what your body reacted to.
Can I compare my HRV with other people?
No. HRV varies enormously between healthy people, so a single score cannot be compared with someone else. The useful comparison is you against your own baseline.
Does HRV diagnose anything?
No. HRV is a non-specific measure of autonomic state. It does not identify, confirm or rule out any condition. Anything clinical belongs with a doctor.
Where do I start?
Book a free consultation. We will arrange the sensor fitting at the studio on Sukhumvit Soi 23, Asok.