Measuring activity using actometers: A methodological study

Actometers are men's self-winding mechanical wristwatches that have been modified such that they measure activity rather than time. Actometers can be used to obtain longitudinal naturalistic measures of activity concerning a variety of clinical populations. However, no systematic methodological research has been conducted with regard to the site of attachment and the duration of measurement necessary to ensure valid results. This article presents the results of a methodological study designed to answer these questions. The mean activity levels associated with the Left Wrist and Ankle were nearly equal to those associated with the Right Wrist and Ankle. The Ankle readings were substantially greater than the Wrist readings because the subjects' legs were longer than their arms. The data from Week 2 were the same as those from Week 1.