Mosaic Score is an iOS app that reads your Apple Watch data — HRV, training load, sleep, resting heart rate, VO2 Max, and wrist temperature — and produces a single daily number showing how close you are to your personal fitness peak. All processing happens on your iPhone. Nothing is uploaded to external servers.
The score is built on published sports science methodology: TRIMP for training load quantification (Banister, 1975), ACWR for workload balance (Gabbett, 2016), and HRV-based recovery tracking. Each signal is measured against your personal baseline — the best levels your Apple Health data has actually observed — not a population average. Below is a breakdown of every signal and how it contributes to your score.
What it is: A single number — 0 to 100 — reflecting how close you are to your personal peak across every signal Mosaic Score tracks.
What makes it different: Most health scores compare you to a population average. Your Mosaic Score compares you to you — specifically, to the best version of yourself the data has actually observed. That's a fundamentally different question, and a fundamentally more honest answer.
What it looks like in practice: Below your score, Mosaic Score shows you the ranked drivers — the signals that moved the most and pulled your number in either direction. Not just a number. A reason.
When it updates: Your Mosaic Score recalculates each morning using the previous night's recovery data and your most recent training history. It reflects where you are right now — not where you were mid-workout. Think of it as your morning briefing, not a live ticker.
This is what your morning briefing looks like. Sleep cost you today. Your heart rate signals are holding strong. The number tells you where you are — the drivers tell you why.
What it is: A way of measuring how hard a workout actually was on your body. Not just how long. Not just how fast. How hard — weighted by intensity.
The plain English version: Thirty minutes at a casual pace is not the same as thirty minutes at your limit. TRIMP accounts for this. Time spent at high heart rate counts for significantly more than time spent at low heart rate — because that's how your body actually experiences effort.
The origin: Sports scientist Eric Banister developed this framework in the 1970s. It remains a gold standard for quantifying training stress because it reflects physiological reality, not just elapsed time.
Your calendar said the same thing on both days — 40 minutes of activity. Your body did not have the same day. TRIMP is how Mosaic Score tells the difference.
Mosaic Score uses TRIMP to understand your effort history — not to tell you how hard to train.
What it is: A comparison between what you've done in the last 7 days versus your average over the last 4 weeks.
The plain English version: Your body adapts to training over time. Your 4-week average represents what it's currently prepared for. Your 7-day load represents what you're asking of it right now. The ratio between them is a signal worth watching.
What the research suggests: A ratio in the moderate range generally reflects training within your current capacity. Ratios significantly above that range have been associated with increased injury risk in athletic populations. The ranges shown below are drawn from published research on athletic populations and are intended as general context — not individual thresholds.
This is a population-level research signal applied to your individual data. It's context, not a verdict.
Mosaic Score shows you where this ratio sits. It does not tell you what to do with that information.
What it is: The variation in time between consecutive heartbeats. Higher variability generally reflects a nervous system that's recovered and ready. Lower variability is often a sign of accumulated stress — physical, emotional, or both.
Why it matters more than resting heart rate alone: Resting heart rate tells you roughly how hard your heart is working. HRV tells you how well your body is adapting. It's one of the most sensitive signals available through consumer wearables — and one of the most frequently misread. Mosaic Score tracks your personal HRV trend, not a population benchmark. A score of 42ms means something very different for you than it does for the next person.
Where the number comes from: Your Apple Watch measures HRV using SDNN — standard deviation of NN intervals, a standard statistical measure of beat-to-beat variation — captured during your overnight sleep. Mosaic Score reads this from Apple Health.
Mosaic Score tracks your trend — not whether your number is "good." A consistent trend matters more than any single night's reading.
HRV is highly individual. Mosaic Score never compares your HRV to population norms — only to your own history.
What Mosaic Score tracks: How long you actually slept (versus time in bed), how efficient that sleep was, and whether you're building or repaying a sleep debt over time.
Why it's not just a bedtime: Eight hours in bed isn't eight hours of sleep. Sleep efficiency — the ratio of actual sleep time to time in bed — tells you whether your body is getting the recovery it expects. A consistently low efficiency score is meaningful even when total duration looks fine.
Sleep debt: Your body keeps a running tab. One short night is recoverable. Chronic shortfall accumulates. Mosaic Score tracks your rolling sleep balance so you can see whether you're ahead or behind — and whether this week's fatigue has a simple explanation.
You're 42 minutes behind your baseline need this week. Not a crisis — but it's showing up in your HRV and your Mosaic Score.
Sleep data comes from Apple Health, sourced from Apple Watch. Mosaic Score does not interpret your sleep stages as medical findings.
Three signals that tell the same story from different angles: how well your body is adapting over time.
Resting HR trending down while VO2 Max holds steady — you're recovering well. Wrist temp slightly elevated — one signal worth watching over the next few nights.
Resting Heart Rate is one of the most reliable long-term fitness markers available. A downward trend over weeks reflects improving cardiovascular efficiency. Day-to-day spikes often precede or follow illness, stress, and overtraining.
VO2 Max is the gold standard estimate of aerobic capacity — how efficiently your body uses oxygen during exercise. Apple Watch derives this during outdoor runs and walks. Indoor workouts are not currently used by Apple for this estimate, so users who train primarily indoors may see this metric update less frequently. Mosaic Score tracks your trend over time, not just the latest reading.
Wrist Temperature is measured nightly by Apple Watch Series 8 and later. Deviations from your personal baseline — even small ones — often precede illness or signal accumulated fatigue before other metrics move. Mosaic Score shows you the deviation, not just the raw reading.
These readings come from your wearable devices and are not clinically validated. Mosaic Score uses them as relative signals — trends over time, not absolute values.
What it is: Not a chart average. Not a population benchmark. The peak that your data has actually demonstrated — across all signals, over time. This is the reference point every Mosaic Score is measured against.
Why it matters: Knowing you scored a 74 means almost nothing without context. Knowing you scored a 74 when your personal peak is 91 — and that you've been trending away from it for 11 days — means something real.
How Mosaic Score builds it from day one: Most apps start cold. You install them, and they know nothing about you. They need weeks — sometimes months — before they have enough history to establish any kind of baseline.
Mosaic Score works differently. At first launch, it scans up to 365 days of your Apple Health history. Because your data was already there — from your Apple Watch, your workouts, your sleep — Mosaic Score arrives knowing you. Your baseline is built from real peaks your body has already demonstrated, not estimates, not projections.
Most apps would show you a blank screen on day one. Mosaic Score shows you a year of context.
How the baseline updates: Your baseline isn't static. As you train, recover, and improve, Mosaic Score updates your peak reference point. When you surpass your previous best — that becomes the new ceiling.
Mosaic Score is not a medical device. It doesn't diagnose conditions, prescribe training plans, or tell you what your numbers mean for your health. These signals were selected because they have legitimate research foundations in exercise science and recovery physiology. We surface them because we believe you deserve to see real data about your own body — not just a colored circle and a mood emoji.
What you do with that information is up to you.
Mosaic Score is an iOS health analytics app that gives you a single daily number — 0 to 100 — showing how close you are to your personal fitness peak. Unlike generic health scores that compare you to a population average, Mosaic Score compares you only to your own best. It reads from Apple Health and processes everything entirely on your iPhone.
Mosaic Score requires an iPhone running iOS 17 or later. An Apple Watch is strongly recommended — it provides HRV, resting heart rate, sleep analysis, wrist temperature, and VO2 Max estimates. Apple Watch Series 4 or later is supported. Wrist temperature requires Series 8 or later.
No. Mosaic Score processes all health data entirely on your device. Nothing is uploaded to external servers. Your health data is read from Apple Health, analyzed locally, and never transmitted anywhere. The only external data Mosaic Score sends is anonymized usage analytics via TelemetryDeck — which contains no health information.
Your score is a composite of five signal categories: training load (using TRIMP and ACWR), heart rate variability, resting heart rate, sleep quality and duration, and overnight signals including wrist temperature and VO2 Max trend. Each signal is measured against your personal baseline — the best levels your own data has actually observed. The result is a 0–100 score that reflects where you are relative to your own peak.
Your personal baseline is the peak performance level your Apple Health data has actually demonstrated across all signals over time. At first launch, Mosaic Score scans up to 365 days of your existing health history and identifies your peak windows. This means the app arrives knowing you on day one — no waiting weeks before it becomes useful. Your baseline updates automatically as you improve and set new personal bests.
TRIMP (Training Impulse) is a method for quantifying workout stress developed by sports scientist Eric Banister in 1975. It weights time spent at different heart rate intensities — 30 minutes of high-intensity interval training scores far higher than 30 minutes of easy jogging, reflecting the actual physiological demand on your body. Mosaic Score uses TRIMP to measure true training load rather than just elapsed time.
ACWR (Acute:Chronic Workload Ratio) compares your training load over the last 7 days to your average over the last 28 days. A ratio in the balanced range (0.8–1.3) means your recent training is consistent with what your body is prepared for. Higher ratios reflect a spike in load relative to your baseline capacity. Research on athletic populations associates significantly elevated ratios with increased injury risk. Mosaic Score shows your ACWR as context — not a prescription.
Your Mosaic Score updates each morning using the previous night's recovery data and your most recent training history. Changes are driven by sleep quality, HRV fluctuations, training load changes, and natural variation in recovery signals. A drop typically reflects accumulated fatigue or a recovery signal moving below your baseline. The driver breakdown beneath your score shows exactly which signals moved and in which direction.
No. Mosaic Score is a general wellness app. It is not a medical device and does not diagnose, treat, or prescribe anything. The signals it tracks are grounded in published exercise science research and are intended to give you a clearer picture of your own data — not to replace professional medical judgment.
Mosaic Score offers a 14-day free trial with full access. After the trial: $7.99/month or $59.99/year. A one-time lifetime purchase is also available at $149. All pricing is in USD and billed through the App Store.
Apple Health and Apple Fitness aggregate your data and display today's numbers. Mosaic Score adds what Apple doesn't provide: your personal baseline and a composite daily score showing where you stand relative to your own best performance. Apple shows you the data. Mosaic Score answers the question Apple can't — how far you've come and how close you are to where you used to be.
Setup takes about two minutes. After granting Apple Health access, Mosaic Score scans your existing health history — up to one year — and builds your personal baseline automatically. Most users have a fully calibrated score within 2–3 minutes of first launch, with no manual configuration required.
Mosaic Score is coming to the App Store. Questions? Contact support.