# Resting HRV Protocol

## Overview

The resting protocol evaluates recovery, fatigue, and autonomic nervous system
balance using heart rate variability (HRV). It provides a stable, reproducible
daily reference that feeds the personal baseline.

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## Principle

The protocol relies on measuring heart activity in a fully rested state to
obtain a stable, consistent reference that can be compared across sessions.
Results are only meaningful when the measurement conditions remain constant
over time.

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## Recommended measurement frequency

| Frequency    | Quality          |
| ------------ | ---------------- |
| 1× / week    | too sparse       |
| 3× / week    | acceptable       |
| 1× / day     | optimal          |

HRV varies significantly from day to day. A single isolated measurement is
unreliable. The trend across multiple sessions is what drives actionable insights.

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## When to measure

* Immediately **upon waking**, before getting out of bed.
* Before talking, checking your phone, or drinking coffee.

Morning measurements capture the body's baseline autonomic state before any
external stimuli alter it.

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## Position

Choose one position and keep it consistent across all sessions:

* **Lying down** (recommended) — minimises cardiovascular load.
* Seated — acceptable if lying down is not practical.

Do not alternate positions between sessions: posture significantly affects
absolute HRV values and would invalidate baseline comparisons.

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## Duration

| Duration     | Assessment     |
| ------------ | -------------- |
| 1 minute     | minimum        |
| 5 minutes    | recommended    |
| 5–10 minutes | optimal        |

Recordings shorter than 5 minutes may produce unreliable frequency-domain
estimates (LF/HF), because the low-frequency band (0.04–0.15 Hz) requires
at least 25 seconds to be observed and ideally several full cycles.

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## Breathing

* Breathe naturally — do not control or regulate breathing pace.
* Controlled breathing (e.g. 6 breaths/min) shifts HF power and is
  appropriate only for specific resonance-frequency protocols, not for a
  standard resting baseline.

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## What to avoid

* Movement or postural changes during the recording.
* Mental stress or stimulation immediately before measuring.
* Loud noise or bright light.
* Recording within 2 hours of exercise or a heavy meal.

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## Interpreting results

### RMSSD

* ↑ increases → good recovery
* ↓ decreases → fatigue or cumulative stress

### Heart rate

* Lower than usual → effective rest
* Higher than usual → stress, illness, or incomplete recovery

### General rule

Absolute values matter less than their deviation from your personal baseline.
A RMSSD of 40 ms may be excellent for one individual and below average for another.

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## Validity conditions

A measurement is considered reliable when:

* Recording conditions are consistent with previous sessions.
* Duration is at least 1 minute (5 minutes recommended).
* The sensor had stable contact throughout (no motion artefacts).

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## Summary

The resting protocol is simple but powerful. Its value accumulates over time:
the more consistent sessions are recorded, the more accurate and personalised
the baseline becomes.
