How does this day compare?
Eligible daily HRV and resting heart rate against earlier days. An early read is labelled. A retained result keeps its original time.
How it works
Insight starts
with context.
A measurement is useful when you know where it came from, what it’s compared with, and what it can’t tell you.
Your source
Records available readings
Apple Health
Shares with your permission
Resile on iPhone
Builds personal context
Read-only access. No direct wearable account login. No Health upload to Resile.
Your history comes first
Compared with you.
Not everyone else.
Today uses eligible daytime HRV and resting heart rate from the same source. Earlier daily readings create a personal reference, so the comparison reflects your history.
The daily HRV reference uses earlier days in a 30-day window; resting heart rate uses a 60-day window. Each relevant reference needs at least 14 prior days. Existing Health history counts.
These windows, evidence thresholds and state labels are Resile’s engineering choices. Published research does not validate those exact cutoffs or certify the app’s stress interpretation.
Three views.
Three different questions.
What does the recent window show?
Suitable resting readings over a shorter window. It has its own evidence time and can differ from the day’s pattern.
What was actually received?
The latest HRV and resting heart rate, with units and time. Receiving a value does not automatically make it eligible for every interpretation.
Measurement, explained
A clearer look
at HRV.
RMSSD and SDNN are different.
Resile calculates RMSSD from available heartbeat-series intervals. Apple Health’s stored HRV quantity is SDNN. Both are expressed in milliseconds, but they use different calculations and should not be treated as interchangeable. Apple’s SDNN documentation.
Gaps stay gaps.
The primary calculation does not join valid intervals across missing beats. The app may show a separately named gap-bridged number in details for reconciliation; that number does not drive the interpretation.
A physiological pattern is not an emotion.
Readings need context. Resile does not diagnose emotional stress or tell you why a pattern changed. General wellbeing is the purpose, and uncertainty remains part of the explanation.
Read the sources
Evidence you can inspect.
The app includes an evidence library with source notes and limitations. Here are useful starting points.
Measurement guidance
Guidelines for measuring heart rate and HRV
Methodological guidance on recording, context and transparent reporting—not validation of Resile’s thresholds.
Apple HealthKitReading heartbeat-series samples
How apps query available heartbeat data. Reading a series does not start a new sensor measurement.
Reference dataMIT-BIH reference heartbeats
A way to check heartbeat calculations. It cannot establish real-world emotional-stress accuracy.
Explore the detail. Keep the perspective.
No account. No subscription. Just a clearer view.