Measurement of activity.

Activity is a phenomenon of concern to nursing. Although a wide variety of instruments have been used to measure activity, researchers have confronted barriers to its measurement in reliable, valid, and practical ways. Technological advances have stimulated theoretical and empirical developments in the study of activity by improving the physical instrumentation. This article presents an overview of methods used to measure human activity, with an emphasis on technological advances and the methods relevant to nursing. Self-report, behavioral observation, and mechanical and electronic activity measures are reviewed and critiqued.