Glossary

If the app shows you a word and you are not sure what it means, it should be here. If it is not, that is a gap worth telling us about.

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Sleep

Sleep score — a single number for the quality of one night. The Workbench can show one of two: the vendor’s own (your Oura or Polar score), or its own calculation. Which one you see depends on your source and your settings. SHI (Sleep Health Index) — a score for your sleep over the last four weeks rather than one night. It weighs regularity, duration and continuity together. Needs 14 usable nights inside a 28-night window before it shows anything at all; until then it reports progress, not a number. SRI (Sleep Regularity Index) — how consistent your sleep timing is. Going to bed at 11pm most nights scores high; a schedule that swings by hours scores low. Feeds into SHI. Hypnogram — the coloured chart of your night, showing which stage you were in at each point. Sleep stages — Deep (physical restoration), REM (dreaming, memory), Light (the majority of the night), Awake (brief wakings, entirely normal). TST (Total Sleep Time) — how long you were actually asleep. TIB (Time in Bed) — how long you were in bed, asleep or not. Always longer than TST. Sleep efficiency — TST divided by TIB, as a percentage. Roughly, how much of your time in bed was spent asleep. Above about 85% is typical. SOL (Sleep Onset Latency) — how long you took to fall asleep. Also shown as Time to sleep. Apple Watch cannot provide this; see Apple Health. WASO (Wake After Sleep Onset) — total time awake after first falling asleep, excluding the final waking. Sleep debt — accumulated shortfall against what your body appears to need. Computed but not shown in this build.

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Body and effort

Capacity — the Workbench’s estimate of how much your body has available today, from your recent sleep, recovery and load. Higher means more in the tank. Still being calibrated. Activity Units (AU) — effort normalised so different activities compare sensibly. A hard swim and a hard run should produce similar AU even though the raw numbers look nothing alike. Training Load — accumulated training stress, in the tradition of published load models. Rises with hard sessions, decays with rest. Borg RPE — a self-rated effort scale where you say how hard something felt. The Workbench uses a 1–10 scale. Subjective on purpose: your sense of effort carries information no sensor has. Zone 2 — a training intensity you could sustain while holding a conversation with mild difficulty. Widely used in endurance and longevity training. Cumulative Stress — accumulated physiological load over recent days.

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Heart and breathing

HRV (Heart Rate Variability) — variation in time between heartbeats. Higher generally means better recovery. Extremely sensitive to alcohol, illness, late meals and strap tightness, which is why it should be read as a trend. See Why we read trends. RMSSD and SDNN — two different mathematical ways of measuring HRV. They are not interchangeable, and the Workbench keeps them apart. Resting HR — heart rate at complete rest, usually taken overnight. One of the most useful single numbers a wearable produces. Heart-rate dip — how far your heart rate falls overnight compared with your daytime baseline. A good dip suggests a night spent recovering. SpO₂ — blood oxygen saturation, as a percentage. Normally 95–100%. Respiratory rate — breaths per minute, usually measured while asleep.

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Body composition

Body fat % — proportion of your body that is fat. BIA (Bioelectrical Impedance Analysis) — how smart scales estimate body composition, by passing a tiny current through you. Convenient, and sensitive to hydration — which is why the trend matters more than any single reading. DEXA — a clinical scan, the reference standard for body composition. If you have had one, the Workbench can use it to correct your scale’s bias. Metabolic Age — how your metabolism compares with population norms for your age. Needs both weight and body fat percentage. Vascular Age — how your arteries compare with population norms, estimated from blood pressure. A hand-logged reading is enough; no special hardware needed. PWV / ePWV (Pulse Wave Velocity) — how fast the pressure wave travels along your arteries. Faster suggests stiffer vessels. ePWV is the estimated form, derived from blood pressure and age. BMR (Basal Metabolic Rate) — calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) — total calories burned in a day, including everything you did. Basal vs Active calories — basal is the burn that happens anyway; active is what you added by moving.

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Glucose

CGM (Continuous Glucose Monitor) — a sensor worn on the skin that reads glucose every few minutes. Ottai is the only one supported end-to-end here. mmol/L and mg/dL — two units for the same thing. The UK, NZ and much of Europe use mmol/L; the US uses mg/dL. Switchable in settings. Time in Range (TIR) — the proportion of readings inside a healthy band. GMI (Glucose Management Indicator) and eA1c — two ways of estimating long-term average glucose from CGM data. They use different published formulas and give different numbers, which is why the app labels which it is showing. Ketones — produced when your body burns fat for fuel. Rise during fasting or on a very low-carbohydrate diet. Lumen — a handheld device that estimates whether you are burning mostly fat or mostly carbohydrate, from your breath.

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Cycle

Cycle day — days since your period started, counting the first day of full flow as day 1. Cycle phase — Menstrual, Follicular, Ovulation, Early luteal, Late luteal, Premenstrual. Estimated from your own cycle length once enough is logged, and from a 28-day default before that.

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The app itself

Source — where a measurement comes from. Apple Health, Oura, Polar and so on. See How sources work. Primary source — the source the app trusts by default when several could answer. Discovery — the screen that asks each source what it can actually provide. See Discovery and Send to VT. Eir — the app’s explanation feature. Tapping the Eir circle asks for a plain-language reading of what a screen is showing. Night Log — an optional way to record night wakings by tapping once, without properly waking up. Off by default. Baseline — your own normal, learned over time. Most figures are compared against yours, not against a population. Deviation — how far today sits from your baseline. Often more meaningful than the raw number. Vitality Score and Symptoms — platform features that do not produce results in this build. See What works, what does not.