A glossary of health & sensors
Short, plain-language definitions of the terms you'll meet across WITU — from ECG and HRV to the DCI index. Each term links to a deeper explainer.
Key terms, explained simply
- ECG (electrocardiogram)
- A recording of the heart's electrical activity. An ECG shows the rhythm and shape of each heartbeat and helps detect arrhythmias — unlike an optical pulse, it measures the heart's electrical signal directly.Learn more →
- Dual ECG
- WITU's approach of capturing the signal across two leads at once. Two independent channels raise the confidence of a recording and make it easier to reject motion artefacts.Learn more →
- PPG (photoplethysmography)
- An optical method: an LED illuminates the skin while a sensor measures changes in blood flow. PPG yields heart rate and blood-oxygen saturation, but is more sensitive to motion than ECG.Learn more →
- HRV (heart rate variability)
- The variation in time between consecutive heartbeats. High HRV usually signals good recovery and a balanced nervous system, while low HRV points to stress or fatigue.Learn more →
- DCI (Data Confidence Index)
- WITU's proprietary metric (Data Confidence Index) that scores the quality of each measurement. DCI tells you how much to trust a given reading and whether noise may have distorted it.Learn more →
- SpO₂ (oxygen saturation)
- The percentage of oxygen carried in the blood, measured optically (PPG). Values around 95–99% are typical; a sustained drop can point to a breathing or sleep problem.Learn more →
- EDA (electrodermal activity)
- Changes in the skin's electrical conductance driven by sweat-gland activity. EDA reflects the nervous system's response and is used as a marker of stress and emotional arousal.Learn more →
- Recovery Score
- A single readiness score for the day. It combines HRV, resting heart rate and sleep to help you decide whether to train hard or take it easy.Learn more →
- VO₂max
- Maximal oxygen uptake — a measure of aerobic endurance and overall fitness. The higher your VO₂max, the more efficiently your body uses oxygen under load.Learn more →
- Holter monitoring
- A long, continuous ECG recording (typically a day to several days) taken during everyday life. Holter monitoring helps catch rare or intermittent rhythm disturbances that a brief test would miss.Learn more →
- Dry electrodes
- Electrodes that record an ECG without conductive gel. They suit wearables and everyday measurements, though they need firm skin contact for a clean signal.Learn more →
- Atrial fibrillation
- A common rhythm disorder in which the upper chambers of the heart beat chaotically and irregularly. Early detection by ECG matters, because untreated atrial fibrillation raises the risk of stroke.Learn more →
WITU is a wellness device, not a medical device
Insights are provided for general wellness and informational purposes only and are not intended to diagnose, treat, or replace professional medical advice. If you have any health concerns, consult a qualified healthcare provider.