Background: Because physical activity researchers are increasingly using objective portable devices, this review describes the current state of the technology to assess physical activity, with a focus on specific sensors and sensor properties currently used in monitors and their strengths and weaknesses. Additional sensors and sensor properties desirable for activity measurement and best practices for users and developers also are discussed.
Best Practices: We grouped current sensors into three broad categories for objectively measuring physical activity: associated body movement, physiology, and context. Desirable sensor properties for measuring physical activity and the importance of these properties in relationship to specific applications are addressed, and the specific roles of transducers and data acquisition systems within the monitoring devices are defined. Technical advancements in sensors, microcomputer processors, memory storage, batteries, wireless communication, and digital filters have made monitors more usable for subjects (smaller, more stable, and longer running time) and for researchers (less costly, higher time resolution and memory storage, shorter download time, and user-defined data features).
Future Directions: Users and developers of physical activity monitors should learn about the basic properties of their sensors, such as range, accuracy, and precision, while considering the data acquisition/filtering steps that may be critical to data quality and may influence the desirable measurement outcome(s).
1Diabetes, Endocrinology, and Obesity Branch, Intramural Research Program, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD; 2Department of Health and Human Physiology, College of Liberal Arts and Sciences, University of Iowa, Iowa City, IA; and 3Department of Kinesiology and Community Health, College of Applied Health Sciences, University of Illinois at Urbana-Champaign, Urbana, IL
Address for correspondence: Kong Y. Chen, Ph.D., National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 10-CRC, Rm 6-3940, 10 Center Dr., Bethesda, MD 20892; E-mail: firstname.lastname@example.org.