Fifty points for what you do. Fifty for how your body responds.
Most health scores measure one or the other. Effort alone flatters you on a week you trained hard and slept four hours a night. Physiology alone tells you where you are but never what to do about it.
The Index carries both halves, deliberately. Behavior is yours to change today. Physiology is the receipt — it moves in weeks, and it's the part you can't talk your way into.
Eleven components. Every one has a weight, a look-back window, and a minimum amount of data before it's allowed to count.
Half one · 50 points
What you do.
Sleep behavior
15 pts · 28 nights
Scores how long you sleep and how consistent your sleep timing is, night to night.
Why consistency is weighted at all: in a UK Biobank cohort of over 60,000 adults wearing accelerometers, day-to-day regularity of sleep and wake timing predicted all-cause mortality more strongly than sleep duration did. Going to bed at the same time is not a nicety layered on top of getting enough hours. It is its own signal.
Windred et al., Sleep, 2024
Cardio
16 pts · 28 days, recency-weighted
Moderate-to-vigorous activity minutes, with recent weeks counting for more than older ones.
Why short sessions still count: the WHO's 2020 guidelines recommend 150–300 minutes of moderate activity per week and removed the old rule that activity had to be accumulated in bouts of at least ten minutes. The evidence showed shorter bouts carry benefit too. A twenty-minute session is real cardio, and the Index scores it as such.
World Health Organization, Guidelines on physical activity and sedentary behaviour, 2020
Strength
14 pts · 28 days, recency-weighted
Resistance sessions, read from your workout history.
Why it's weighted near cardio, and why more isn't always better: a meta-analysis of 16 cohort studies found muscle-strengthening activity associated with a 10–17% lower risk of all-cause mortality, cardiovascular disease and total cancer — independent of aerobic exercise. The curve is J-shaped: the lowest risk was observed at around 40 minutes per week, and beyond roughly 140 minutes the evidence no longer shows added benefit.
Momma et al., British Journal of Sports Medicine, 2022
Movement
5 pts · 7 days
Daily steps — the background activity that happens outside anything you'd call a workout.
Weighted lightest of the four on purpose. Steps are the easiest signal to accumulate and the least specific about intensity, so they support the score rather than carry it.
Three bonuses, worth up to 11 more
These sit on top of the fifty. They reward habits with real evidence behind them, without punishing anyone who doesn't practice them — you are never marked down for a bonus you don't pursue.
Mindfulness · up to +3Logged mindful minutes and mind-body sessions, over 14 days.
Cold exposure · up to +5Weekly average cold-exposure time, over 14 days.
Hydration · up to +3Consistency against your own daily water goal, over 14 days.
Half two · 50 points
How your body responds.
Heart adaptability
20 pts · 14-day vs 60-day medians
Heart rate variability and resting heart rate, each read as your recent two weeks against your own two-month baseline.
Why it's the single heaviest component: in the Framingham Heart Study, reduced heart rate variability was associated with increased risk of new cardiac events in adults with no clinically apparent heart disease at baseline. It is one of the few things a wrist wearable measures nightly that has this depth of outcome data behind it.
Why it compares you to yourself: absolute HRV values vary enormously between people — a healthy 30 ms and a healthy 90 ms both exist. The sports-science literature on monitoring training status treats the meaningful signal as change against an individual's own rolling baseline, not a population number. That's how the Index reads it.
Tsuji et al., Circulation, 1996 · Plews et al., Int J Sports Physiol Perform, 2013 · Buchheit, 2014
Cardio fitness (VO2 max)
15 pts · 90-day median + 14-day trend
Your estimated VO2 max, converted to a percentile against adults of your age and sex — then checked for which direction it's moving.
Why fitness earns 15 points: across 122,007 adults undergoing treadmill testing, cardiorespiratory fitness was inversely associated with all-cause mortality with no observed upper limit of benefit. Fitter kept being better, all the way up. There was no point in the data where additional fitness stopped helping.
Mandsager et al., JAMA Network Open, 2018
Restorative sleep
10 pts · 14 nights
REM and deep sleep — the stages, not the hours. This is the physiological counterpart to the behavior half's sleep score: one measures whether you gave yourself the chance to sleep, this one measures what your body did with it.
Body composition
5 pts · current
BMI, from your height and weight. Weighted lightest of the four, because BMI is a blunt instrument at the individual level — it cannot tell muscle from fat. It earns a small place in the Index and nothing more.
One component, in full
How a VO2 max becomes a percentile.
A raw VO2 max of 41 means nothing on its own. For a 25-year-old man it's unremarkable. For a 65-year-old woman it's exceptional. The number only becomes information once it's placed against people like you.
synqology maps your 90-day median VO2 max onto reference standards from the Fitness Registry and the Importance of Exercise National Database — FRIEND — a multi-laboratory registry of maximal exercise tests in adults aged 20 to 79 without cardiovascular disease, published as percentile tables by decade and sex.
So the component doesn't ask "is 41 good?" It asks "where does 41 put you among adults your age and sex?" — and then, separately, "which way has it moved in the last two weeks?"
Kaminsky et al., FRIEND registry reference standards, Mayo Clinic Proceedings
What the Index is not.
It is not a prediction of how long you'll live. The research behind each component describes associations across large populations. It does not forecast an individual outcome, and neither does your score.
It is not a diagnosis. synqology is a wellness product. It doesn't detect, diagnose, or treat disease, and it isn't a substitute for a clinician who knows your history.
It is not fixed. When the evidence moves, the Index moves with it — and the app tells you what changed and why, rather than silently re-scoring your past.
