actimeters

An actimeter is a device used to measure bodily movement for research and clinical purposes. Modern actimeters are typically worn on the wrist or other body sites and rely on accelerometers to record the intensity and timing of movement over time. They may store data onboard or transmit it wirelessly for later analysis. In practice, actimeters are often referred to as actigraphy devices, and the resulting data are described as actigraphic recordings.

Data from actimeters are usually summarized into epochs, such as 30-second or 1-minute intervals, producing metrics such as activity counts, movement intensity, and patterns over the day. Common analyses include sleep-wake classification, estimations of circadian rhythms, and proxies for overall physical activity or energy expenditure. While actimeters can indicate when movement occurs and its relative intensity, they provide only indirect estimates of energy use and do not capture context, form of activity, or exact energy expenditure without calibration.

Applications of actimeters span sleep research, pediatric and clinical monitoring (for disorders such as insomnia, ADHD, or autism), rehabilitation and chronic disease management, and ergonomics. They are also used in animal studies to quantify locomotor activity. Limitations include potential misclassification of sleep versus quiet wakefulness, non-wear periods, and reduced accuracy when movements are limited or repetitive. Validation against criterion measures such as polysomnography is common in clinical settings.