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Two metrics, one picture
RMSSD
Your parasympathetic "rest & digest" tone — how well your body recovers overnight. The most sensitive short-term stress marker.
Oura Ring
Apple Watch
Garmin
Polar
SDNN
Total autonomic flexibility — the full range of both sympathetic and parasympathetic activity. A wider range means better adaptability.
Apple Watch
Garmin
Polar
HRV — 7-day trend
RMSSD overnight readings vs personal baseline
The four states
Autonomic State Map
Where your SDNN and RMSSD combination places you today
Q1
Balanced Recovery
High SDNN · High RMSSD
Q2
Sympathetic Dominance
High SDNN · Low RMSSD
Q3
Low Variability
Low SDNN · High RMSSD
Q4
Autonomic Exhaustion
Low SDNN · Low RMSSD
← LOW SDNN
RMSSD ↑↓
HIGH SDNN →
Q1
Balanced Recovery
High SDNN + High RMSSD
Both branches of your autonomic system are working well together. Your body is flexible, well-regulated, and ready to handle whatever the day brings. This is the state your nervous system is aiming to return to every night.
Today
Good window for Zone 2 cardio, strength training, or demanding cognitive work. Your body will adapt well. Maintain your routine — whatever you're doing is working.
Glucose
Insulin sensitivity tends to be better on high-HRV days. Expect flatter post-meal curves, less glucose variability, and less correction needed throughout the day.
Q2
Sympathetic Dominance
High SDNN + Low RMSSD · "Wired but tired"
Your system has energy and range, but the parasympathetic recovery brake isn't engaged. Common after poor sleep, emotional stress, high caffeine, or a demanding training block.
Today
Skip intense exercise — opt for a walk, slow breathwork (box or 4-7-8 breathing), or gentle yoga. Reduce caffeine. Avoid adding more stressors.
Glucose
Sympathetic dominance elevates cortisol, which raises blood glucose. Expect a higher fasting number and more reactive post-meal spikes.
Q3
Low Variability
Low SDNN + High RMSSD · Rare pattern
Total autonomic range is reduced while the parasympathetic system remains active — sometimes called a "freeze" or withdrawal response. Also appears with beta blockers, sedatives, or certain SSRI adjustments.
Today
Gentle activation helps more than deep rest. Light movement, social engagement, and grounding activities. Note any recent medication changes.
Glucose
Reduced autonomic range can blunt the body's normal glucose regulatory response. Finger-check more frequently, especially around meals.
Q4
Autonomic Exhaustion
Low SDNN + Low RMSSD
Both branches of your autonomic system are suppressed. Associated with burnout, illness onset (often 1–2 days before symptoms), acute trauma flares, and elevated cardiac risk. Take this seriously.
Today
Reduce all non-essential demands. No hard exercise, no major decisions. Prioritise sleep above everything. If this persists 3+ consecutive days, consult your healthcare provider.
Glucose
Highest-risk HRV state for glucose control. Autonomic exhaustion significantly impairs insulin sensitivity — expect elevated fasting glucose and higher post-meal variability.
The SDNN/RMSSD ratio
Reading the balance
Dividing SDNN by RMSSD reveals which branch is dominant — even when absolute values appear within your normal range. A rising ratio over several days is an early warning signal worth acting on.
0.8 – 1.2
Parasympathetic dominant — deep recovery state
Ideal overnight
1.3 – 1.8
Balanced autonomic function — normal daily operation
Healthy baseline
1.8 – 2.5
Sympathetic shifting — stress accumulating
Monitor closely
> 2.5
Significant sympathetic dominance — flag for action
Action needed
HRV state vs glucose variability
Average post-meal glucose excursion by autonomic state (illustrative)
Compatible devices
Where Olakino reads your HRV
◯
Oura Ring
Direct API integration. Provides overnight RMSSD and a 7-day rolling history for baseline calculation.
RMSSD
⌚
Apple Watch
Reads from Apple Health. Provides RMSSD during sleep and Breathe sessions, and SDNN throughout the day. No extra setup beyond enabling Apple Health.
RMSSDSDNN
🏃
Garmin watches
Garmin Connect syncs overnight HRV to Apple Health automatically. No extra setup needed. If both Garmin and Apple Watch are connected, the most recent reading is used.
RMSSDSDNN
🏔️
Polar watches (Vantage V3, Ignite 3, Pacer Pro)
Polar Flow syncs nightly HRV via the Nightly Recharge feature to Apple Health. Same integration path as Garmin — no extra setup needed.
RMSSDSDNN
💓
Polar H10 chest strap
The gold standard for HRV accuracy. ECG-level beat-to-beat RR interval recording — significantly more accurate than optical wrist sensors. Connect via Bluetooth through Polar Flow to Apple Health. Best for dedicated 5-minute morning readings.
RMSSDSDNNMost accurate
💓
Polar H9 chest strap
The affordable sibling of the H10. High-accuracy RR interval recording via Bluetooth. Syncs through Polar Flow to Apple Health the same way as the H10.
RMSSDSDNN
HRV is a self-awareness and tracking tool, not a diagnostic instrument.
Low HRV can reflect many conditions beyond stress — always consult your healthcare provider for clinical decisions.
Individual baselines vary enormously. Compare your values to your own history, not population averages.