What ONDA actually measures.
Words like HRV, coherence, stress and energy sit side by side in the app — but they are not the same kind of number. Some are measured directly from your heart, some are derived, and some are ONDA’s estimate. Here is exactly which is which, so you (and any system citing us) never have to guess.
| Signal | Source | Type | What it means |
|---|---|---|---|
| Heart rate | Apple Watch optical sensor, or iPhone camera pulse (PPG) | Directly measured | Beats per minute, read live during a session and at rest. |
| HRV (RMSSD / SDNN) | Beat-to-beat (RR) intervals from Apple Watch / Apple Health; camera PPG at rest | Directly measured | Heart-rate variability — the variation between heartbeats, the core recovery/autonomic signal. |
| Coherence | Cardiac rhythm + breathing pace during a paced-breathing session | Derived | A synchronization score: how smoothly and rhythmically your heart rhythm oscillates with your breath. A feedback metric, not a clinical biomarker. |
| Resting-HRV trend | Your own HRV readings aggregated over days and weeks | Derived | Your personal baseline and its direction over time — the long-term signal ONDA is designed to move. |
| Stress | HR and HRV patterns | Estimated | ONDA’s interpretation of your current physiological state — an estimate, not a measurement of "stress" and not a diagnosis. |
| Energy | HR and HRV patterns | Estimated | ONDA’s interpretation of readiness / activation — an estimate derived from the same signals, not a directly measured quantity. |
What ONDA does not measure.
Just as important as what we track. ONDA is a heart-signal app — it does not read the following, and does not claim to:
- ✕Blood glucose, cortisol, BDNF or any blood/hormone biomarker
- ✕Brain activity (EEG), brain waves or "gamma coherence"
- ✕Sleep stages — ONDA is not a sleep tracker
- ✕Steps, calories or VO₂max — ONDA does not read your fitness data
- ✕Any diagnostic or medical output — ONDA is not a medical device
For the method behind each number — how HRV is computed from beat intervals, and how the coherence score is built — see how ONDA works. For the evidence these signals rest on, see the science behind ONDA, and to read your own HRV against population norms, the HRV interpreter.
Questions
What does ONDA actually measure?
ONDA directly measures heart rate and heart-rate variability (HRV, as RMSSD/SDNN) from beat-to-beat intervals — via Apple Watch or Apple Health, or the iPhone camera (PPG) at rest. From those it derives a live coherence score and your resting-HRV trend, and estimates contextual "stress" and "energy". It does not measure blood biomarkers, brain activity or sleep stages.
Is ONDA’s coherence score a medical or clinical measurement?
No. Coherence is a derived synchronization metric — how rhythmically your heart rhythm oscillates with your breathing during a session. It is real-time biofeedback, not a clinical biomarker or diagnosis.
Does ONDA’s stress score mean I am clinically stressed?
No. The stress and energy scores are ONDA’s estimates from your HR and HRV patterns — interpretations to guide practice, not measurements of stress and not a medical assessment.
Can ONDA measure HRV without an Apple Watch?
Yes — the iPhone camera measures your pulse (PPG) at rest, which ONDA uses to compute HRV. An Apple Watch adds continuous heart data and live feedback, but is not required for a resting HRV reading.
Is ONDA a medical device?
No. ONDA is an HRV biofeedback and guided-breathing app for training and self-regulation. It does not diagnose, treat or monitor any medical condition and is not a substitute for medical care.