Feasibility of using accelerometers to measure physical activity in young adolescents

Accelerometers may provide valid measures of physical activity, but the feasibility of using accelerometers with large groups of children is unknown. We assessed feasibility in the Eating and Activity Survey Trial (Project EAST), a study designed to develop valid tools to assess eating and physical activity patterns among middle school children.

Two hundred eighty-two Project EAST participants in grades 6-8 wore an accelerometer (Manufacturing Technologies, Inc., Fort Walton Beach, FL) for seven consecutive days. Multiple strategies were employed to encourage compliance and return of the accelerometer: 1) staff demonstrated how to wear the device properly; 2) students were given written and verbal instructions; 3) staff visited the students twice during 7 d to remind them to wear the devices and return them on time; and 4) movie tickets were given to students who returned the accelerometers on time.

Data from 27 accelerometers were lost as a result of mechanical and nontechnical problems, resulting in unusable data for 8.5% of students. Days of data for the remaining 255 students were considered incomplete if the accelerometer registered less than three consecutive waking hours of zero counts. The percentage of students with complete accelerometer data for 3-7 d of data were > or = 3 d, 92%; > or = 4 d, 86%; > or = 5 d, 75%; > or = 6 d, 67%; and 7 d, 50%. Twenty-eight students (10%) returned their accelerometers late. Overweight children were significantly more likely to have 7 d of complete data than nonoverweight children.

Our findings suggest that accelerometers are acceptable to most students. However, researchers working with middle school students should carefully monitor compliance to ensure that devices are worn properly and regularly.