The Objective Monitoring of Physical Activity

Epidemiologists have long recognized the significant limitations of physical activity questionnaires. Advances in the development of objective monitoring devices such as accelerometers have spurred hopes of defining more accurately the relationships between habitual physical activity and chronic disease. As yet, realization of these objectives has been curbed by the failure of accelerometers to record important sources of energy expenditure and the limitation of sample size by labor-intensive checking of output data for artifacts. But in the near future, more complex devices that link the measurement of body accelerations to other phenomena such as posture and GPS location, together with computer-assisted checking of records and processing of data may earn objective monitoring a key place in large-scale epidemiological investigations.