Cardio Adaptability is Body Insights' 14-day view of how your heart settles at night. It pairs Nocturnal HR Dip with sleep heart rate variability, or HRV.
Apple Watch records heart-rate and HRV samples. Apple Health stores the available records. Body Insights reads them, calculates each valid night, and shows the latest result beside the recent trend.
This view is separate from workout pace and VO2 max. It stays focused on your overnight recovery pattern.
What Cardio Adaptability shows
The card starts with last night's result. The history beside it helps you tell a one-off from a pattern.
Latest Nocturnal HR Dip
What you seeA percentage with Strong, Healthy, or Low
What it tells youHow much your average heart rate fell from before sleep to during sleep.
Freshness
What you seeLast Night or Latest Available
What it tells youWhether the headline uses last night's data or the latest valid night.
14-Day Trend
What you seeA short line about HR Dip and HRV moving up, down, or staying steady
What it tells youThe combined direction across recent valid nights.
Nocturnal HR Dip 7d avg
What you seeA percentage
What it tells youYour short-term HR Dip level across valid recent nights.
Sleep HRV 7d avg
What you seeA value in milliseconds when HRV is available
What it tells youYour short-term overnight SDNN level.
Example: 12% and Healthy
A sample result shows a 12% Nocturnal HR Dip with a Healthy status. The 7-day averages are 11% HR Dip and 48 ms sleep HRV. The 14-day line says that HR Dip and HRV are moving up.
The latest value covers the newest valid night. The averages and trend tell you if that result has shown up more than once.
How to use the 14-day trend
Start with the pattern, then compare it with how you slept and how you feel.
After a demanding day
Check the next few valid nights. A return toward your recent averages gives more context than one result taken alone.
When one night looks unusual
Check the freshness label and both charts. A single Low result can sit inside a steady 14-day pattern.
After an evening routine change
Keep the change small and compare similar nights. Wait for the direction to repeat before you change your plan again.
How Body Insights builds the trend
Body Insights uses available records from the latest 14 days.
- It finds each usable sleep period in Apple Health.
- It reads heart-rate samples during sleep and from the two hours before sleep started.
- It calculates the night's Nocturnal HR Dip and reads sleep HRV when it is available.
- It builds 7-day averages and a 14-day direction from the valid nights.
One valid night
The latest result compares your average sleeping heart rate with your average heart rate before sleep. Body Insights then applies the Strong, Healthy, or Low label used in the app.
The 14-day view
The app checks whether HR Dip and sleep HRV are moving up, moving down, or staying steady. It shows the direction in plain language instead of exposing the internal trend thresholds.
When Body Insights needs more nights
The card shows Learning your patterns until it has five valid HR Dip nights. A valid night needs a usable sleep period and enough heart-rate data during sleep and before sleep.
Sleep HRV can stay blank when Apple Health has no usable overnight HRV. The card can still show the HR Dip result after enough nights are valid.
Wear your Apple Watch to bed, let it sync with Apple Health, and check again after more nights. Missing nights stay missing. They do not become zeroes.
See your overnight heart trend
Body Insights turns Apple Health sleep, heart-rate, and HRV records into a result you can inspect night by night.
Check my Cardio Adaptability