The challenges of monitoring physical activity in children with wearable sensor technologies

Physical activity (PA) monitoring in children remains an important challenge for epidemiologists, exercise scientists, clinicians and behavioural researchers as they attempt to utilize PA in combating child-related disorders such as obesity in children and young adults. Work has primarily focused on the development of improved metrics for measuring PA intensity. These metrics have been composed of direct observations, subjective surveys and, recently, portable activity monitors based on inertial sensors (Freedson, Pober, and Janz 2005). Portable monitors using accelerometer sensors have been used since the early 1990s, with development having focused on miniaturization and cost minimization. The challenges in interpreting sensor data as well as calibration and reliability issues have, however, been the focus of research in the last decade (post-2000). Although work is still continuing in the development of models to interpret PA from sensors, field trials have already begun. During 2003–2004, the National Health and Nutrition Examination Survey (NHANES) released survey results of 7000 participants above 6 years of age who wore an accelerometer during the day for 7 days. This large survey concluded that accelerometers could objectively capture physical activities performed by their users; however, inconsistencies with calibration, correlation and validation of sensor measured PA still remain.