Glossary

The words behind recovery, strain and sleep scores, in plain language. Where a term has its own page, the link goes there.

Acute:chronic workload ratio (ACWR): Your average Strain over the last 7 days divided by your average over the last 28. 1.0 means this week matches your usual load. How Pulse uses it
Baseline: Your own normal for a vital, built from earlier nights only: a running average that leans on the last two weeks and clips extreme nights. Pulse compares each night with it rather than with other people.
Energy Bank: A 0-100% estimate of the energy left in your day. It starts from Recovery and sleep, drains with time awake, heart-rate load and stress, and recharges with calm minutes and naps. How Pulse uses it
Fitbit Air: Google's screenless fitness band. It records heart rate, sleep and other vitals and syncs them to the Google Health app, which is where Pulse reads them from.
Google Health API: Google's API for reading a user's health data with their permission. Pulse uses it, with your own Google Cloud OAuth client, to import your Fitbit Air data to your server.
Hazard ratio: How much more or less likely an event (here, death from any cause) is in one group than in a reference group over the same time. Pulse Age turns published hazard ratios into years. How Pulse uses it
Heart rate recovery: How far your heart rate falls in the first minute after a hard effort, in bpm. Larger drops go with better fitness. How Pulse uses it
Heart rate variability (HRV): The variation in time between heartbeats, in milliseconds. Higher than your own baseline usually means your body is coping well; it is not comparable between people. How Pulse uses it
Heart-rate reserve: The gap between your resting and maximum heart rate. Strain measures each minute's effort as a share of it. How Pulse uses it
Illness signal: A flag raised when several vitals (resting heart rate, HRV, skin temperature, respiratory rate) move together in the unwell direction, a pattern often seen early in illness. Not a diagnosis. How Pulse uses it
Max heart rate: The highest heart rate you can reach. Pulse uses the value you set, or estimates it as 208 minus 0.7 times your age. How Pulse uses it
Pace of Aging: How fast your Pulse Age is changing: your last 30 days compared with your last 6 months. Below 1.0x means the recent month looks younger. How Pulse uses it
Provisional: Pulse's label for a score computed before it has enough of your history to be reliable. Pulse shows no number at all when it has too little data, rather than a guess.
Pulse Age: An estimate of how old your body behaves, from nine habits and vitals compared with a fit person of your age and sex. Built on population studies, not a clinical test. How Pulse uses it
Recovery: A 0-100% score each morning of how ready your body is for strain, from HRV, resting heart rate, sleep, respiratory rate and skin temperature against your baselines. How Pulse uses it
Resting heart rate: Your heart rate at rest. Pulse takes the lowest 5-minute average during your main sleep. How Pulse uses it
Restorative sleep: Deep and REM sleep as a share of time asleep. Wrist devices estimate sleep stages only moderately well, so Pulse gives it a modest weight. How Pulse uses it
RMSSD: Root mean square of successive differences between heartbeats: the standard short-term HRV measure, and the one Google Health reports nightly. How Pulse uses it
Self-hosting: Running software on a computer you control instead of a company's servers. Pulse runs as one Docker container, and your data stays in its database volume.
Sleep debt: Sleep you owe from recent nights when you slept less than you needed. Part of it is added to tonight's sleep need. How Pulse uses it
Sleep efficiency: Time asleep as a share of time in bed. How Pulse uses it
Sleep need: How much sleep you need tonight: your usual need from the last 28 nights, plus extra for a hard day and for sleep debt, minus naps. How Pulse uses it
Sleep Regularity Index (SRI): The chance of being in the same state, asleep or awake, at the same clock time on consecutive days, scaled so 100 is an identical schedule. Pulse calls it sleep consistency. How Pulse uses it
SpO2: Blood oxygen saturation, in percent. The Health Monitor flags a night below 95% whatever your usual range. How Pulse uses it
Strain: The cardiovascular load of your day on a 0-21 scale, from minutes spent in heart-rate zones. Each point is harder to earn than the last. How Pulse uses it
Stress (0-3): How far your heart rate sits above your calm daytime level during still, awake minutes, on a 0-3 scale. It reads heart rate only, not how you feel. How Pulse uses it
VO2 max: The most oxygen your body can use during exercise, in ml/kg/min: the standard measure of cardiorespiratory fitness. Google Health gives a value after runs and a daily estimate; Pulse prefers the run value. How Pulse uses it