Under the hood
How the readiness score works.
Your readiness is a single number from 0–100, blended from up to six signals in Apple Health and your own training history. No black box — here's the exact math, the same as it runs in the app.
The formula
Each signal earns points out of its own maximum. The score is the points you earned divided by the points that were available that day (only signals with data count), scaled to 100:
# up to 115 points when every signal has data
readiness = round( earnedPoints / availablePoints × 100 )
Because it normalizes against only the signals present, a day with just sleep and HRV is still scored fairly — you're never penalized for data you didn't record.
The six signals
HRV trend
The slope of your heart-rate-variability trend. Rising HRV means your nervous system is recovering; a steady climb scores near full marks. Falls back to your absolute HRV when there's no trend yet.
Sleep score
Your nightly sleep score (0–100), scaled straight to 25 points. Built from hours slept, deep-sleep percentage and bedtime consistency.
Swim load
Your acute-to-chronic training-load ratio against an ideal band (~0.8–1.3). High volume only costs you if HRV and resting heart rate agree you're straining — and a well-timed taper before a meet earns bonus points.
Resting HR trend
The first-to-last change in your resting heart rate this week. A falling resting HR is a strong recovery signal; thresholds widen with age so younger athletes aren't over-flagged.
Recovery
Consecutive training days measured against your own historical ceiling. A rest day recharges; a block well past your norm nudges the score down.
Practice quality
How much of your recent sessions was active swim time vs. resting on the wall — a proxy for session intensity.
Why it's built this way
Volume alone doesn't mean overreaching. The score cross-checks your training load against real recovery markers, so a heavy week reads as strain only when your body is actually showing it. That's what separates "well-trained and ready" from "dig-yourself-a-hole tired."
A note on honesty
This is a coaching guide, not a medical device. It runs entirely on your device from data you already collect in Apple Health — nothing is uploaded, and the number is only ever as good as the signals behind it. Missing a night of sleep tracking simply drops that signal from the day's math.