Question 1

Why SDNN instead of population standards?

Accepted Answer

SDNN is the primary time-domain measure of heart rate variability that research links to stress load and recovery capacity. But a “normal” range differs enormously between a 25-year-old athlete and a 60-year-old office worker. Tuning anchors every reading to your own 14-day baseline, so a value that looks “average” in a population table can still signal a meaningful shift for you.

Question 2

How does the 14-day rolling baseline work?

Accepted Answer

Tuning only ever stores your own SDNN samples. Day 3 gives an initial assessment, Day 7 establishes a formal baseline, and from Day 14 onward a sliding 14-day window continuously re-baselines. Your readiness is the distance between today’s samples and your personal window — never a fixed population norm.

Question 3

Does Tuning simulate workout recovery?

Accepted Answer

No — this is our core principle. We never fabricate or extrapolate recovery curves. If Apple Health records a new SDNN sample, the chart moves; if it doesn’t, nothing is drawn. What you see is always the real signal from your watch.

Question 4

Is my health data secure and private?

Accepted Answer

Yes. 100% of HealthKit data processing happens on-device. Tuning never uploads, stores, or shares your health data — there is no account database of your readings, and nothing ever leaves your iPhone.

Question 5

How is Tuning's daily readiness score calculated?

Accepted Answer

The readiness score is computed from your own SDNN samples against your personal 14-day baseline. Readings close to or above your baseline suggest your nervous system is balanced and recovering; readings well below it suggest higher stress load. Tuning combines that signal with the number of valid samples that day — a score based on few samples is shown with lower confidence, never guessed.

Question 6

Does Tuning work with my Apple Watch?

Accepted Answer

Tuning reads Heart Rate Variability (SDNN) from the Apple Health app, so it works with any Apple Watch model that records HRV — including watchOS devices from Series 3 onward. Your watch collects the samples passively while Tuning turns them into insight. An iPhone is required.

Question 7

Is Tuning a medical device?

Accepted Answer

No. Tuning is a general wellness app for self-regulation reference only. It does not diagnose, treat, cure, or prevent any disease, and its scores are not clinical measurements. If you have health concerns, always consult a qualified healthcare professional.

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