Science and method
How the numbers are made
Every score is worked out on your phone, and every formula is written down. Here is what goes in, what comes out, and where the limits are.
What goes in
Three signals from your device
Gallen reads these from your strap or ring's own sensors. It adds no sensor of its own.
Heart rate
Through the day and night. Used for strain, zones, resting heart rate and stress.
Beat-to-beat intervals
The tiny gaps between heartbeats. Heart-rate variability (HRV) and breathing rate come from them.
Motion
Used to find when you fell asleep and woke up, and to count steps.
What comes out
Each score in two sentences
Shortened here. The open formulas have every constant and where it came from.
Sleep
The night of a day is the longest sleep that ends on it. Stages are an estimate from heart rate and motion, and labelled as one.
need = 440 min + 4.2 min × yesterday's strain + recent shortfall − naps
Recovery (0 to 100)
HRV, resting heart rate, sleep and breathing are each compared with your own last 30 days, then combined. It needs four nights before it appears.
z = (today − your median) ÷ (1.4826 × spread)
Strain (0 to 21)
Minutes in each heart-rate zone across your waking day are weighted and added up. Logged strength work earns extra credit.
strain = 5.06 × ln(1 + load ÷ 7.02), at most 21
Stress (0 to 3)
Measured only in still, waking minutes: heart rate rising and HRV falling, against your calm level over the last 14 days.
stress = 0.5 × z(heart rate) + 0.5 × −z(HRV), scaled to 0–3
Healthspan trend
Seven habits are scored 0 to 100 over 30 days and averaged. The trend compares the last 30 days with the 30 before.
improving at +3 or more, slipping at −3 or less
Where the constants come from
Fitted to real data, from one person
The formulas follow published research. Several constants were then fitted to one person's own data export from another app: 321 days, 323 sleeps and 334 workouts, joined with 15 days of Gallen's own samples.
That is a start, not a validation. The numbers have not been tested clinically or on other people.
Targets we check against
Targets, not results- HRV
- within 10 %
- Resting heart rate
- within 2 bpm
- Recovery
- within 8 points
- Strain
- within 0.7
- Sleep onset and wake
- within 10 min
Each refit is checked leaving one day out, so it is not tuned to the days it is judged on.
Limits
What Gallen does not claim
Plainly, so you can weigh the numbers for what they are.
- Gallen is not a medical device and does not diagnose, treat or prevent anything.
- The scores have not been validated clinically.
- Strain, recovery and the rest are Gallen's own formulas, not the official formulas of any other app.
- Sleep stages are an estimate.
- The smart alarm uses a heart-rate rule, not sleep stages.
- The healthspan trend is not a biological age.
Be among the first to try Gallen
Android first, iOS later. One email when it is ready, and nothing else.