Health metrics, in plain language

Readiness

Apex Trace's 0–100 estimate of how recovered you are this morning. It compares four signals to your own 30-day baseline: HRV (30%), resting heart rate (20%), last night's Sleep Score (35%), and yesterday's Cardio Load relative to your target (15%). 70 and above reads "go for it"; below 40 reads "take it easy". Formula: methodology §02.

Sleep Score

Apex Trace's 0–100 estimate of last night's sleep quality. It blends how long you slept versus an 8-hour target (50%), the share of the night spent in the restorative deep and REM stages (30%), and restfulness — reduced by awake time and low sleep efficiency (20%). Formula: methodology §01.

Cardio Load

One number for the day's cardio effort: minutes spent in each heart-rate zone, weighted by intensity (Fat Burn ×1, Cardio ×2, Peak ×3) and summed. It's shown against your personal target — your average daily load over the previous 28 days — so "37 / 35" means today edged just past your recent norm. Formula: methodology §03.

Calm

Apex Trace's overnight recovery estimate, used as the recovery axis on the You-screen radar. It reads three overnight signals against your baseline — breathing rate (slower reads calmer), HRV (higher reads calmer), and skin-temperature deviation (closer to normal reads calmer). A typical night sits at the midpoint, and missing sensors simply drop out. Formula: methodology §04.

Body Age (fitness age)

An estimate of your physiological age: the chronological age at which the typical person has the same cardio fitness (estimated VO₂max) as you, based on the US FRIEND/ACSM reference curve. A Body Age lower than your real age means your cardio system is ahead of the curve. Any body measurements you enter stay on your phone and are never transmitted. Formula and sources: methodology §05.

Pace of Aging

The direction your fitness age is moving, not just where it stands: the ratio of your fitness-age change over the last 30 days to the change over the preceding 60 days, centered on 1.0. Above 1 means aging faster than your own recent baseline; below 1 means slowing down. It needs a few months of data to be meaningful. Details: methodology §05.

VO₂max

A standard measure of how efficiently your body uses oxygen during exercise — the most widely used single marker of cardio fitness. Apex Trace estimates it on your device with published non-exercise regression models (Nes et al. 2011 or Jackson et al. 1990), so no exercise test is needed. Models: methodology §05.

Heart-rate variability (HRV)

The variation in the time between consecutive heartbeats, measured in milliseconds. Higher-than-your-normal HRV generally reads as better recovery. Apex Trace always compares your HRV to your own baseline, never to other people.

Resting heart rate (RHR)

Your heart rate at complete rest, in beats per minute. Unlike most signals, a lower-than-your-normal RHR generally reads as better recovery, so Apex Trace scores it in the inverted direction.

Heart-rate zones

Effort bands based on how hard your heart is working — Fat Burn, Cardio, and Peak. Apex Trace uses your minutes in each zone to weight the day's effort when computing Cardio Load, so harder zones count for more.

Sleep stages & hypnogram

The four states a night of sleep cycles through: awake, REM, light, and deep sleep. Deep and REM are the most restorative. A hypnogram is the timeline chart showing when you were in each stage — Apex Trace's Sleep screen draws one for every night.

Sleep efficiency

Time actually asleep divided by time in bed. Spending long stretches in bed awake lowers efficiency, which reduces the restfulness part of the Sleep Score.

Baseline

Your own recent normal: the average of a metric over your previous 30 days. Apex Trace scores you against your baseline rather than against population norms, and needs at least 7 days of data — with less, baseline-dependent scores step aside rather than guessing.

Z-score

How far today's value sits from your baseline, in units of your own day-to-day variation. Zero means a typical day for you; positive means above your normal, negative means below.

All of the above are estimates for general wellness, computed on your device from your own data — not medical measurements, diagnosis, or advice.