Adolescent perspectives on wearing accelerometers to measure physical activity in population-based trials

Background: Accelerometers are increasingly used in health research to measure physical activity, but few published studies document participants’ views and experiences of wearing accelerometers, preferring to focus on measurement decisions and outcomes, and fewer still have reported the views and experiences of adolescent participants. Purpose: The purpose of this study is to examine the use of accelerometers with young people including recruitment, retention and adherence to protocol. Methods: The AHEAD (Activity and Healthy Eating in Adolescence) feasibility study, involving over 1000 students aged 12/13 years, took place in south-west England between 2007 and 2009. Piloting work was followed by an exploratory trial, incorporating a process evaluation, in six schools. Students were asked to wear accelerometers for 7 days at baseline and follow-up. Results: Eighty-nine percent of students provided some accelerometer data at baseline and 87% at follow-up. However, adherence (recording ≥600 minutes per day for ≥3 days) fell from 75% at baseline to 56% at follow-up. Factors affecting adherence included the following: the use and type of incentives, appearance, discomfort and unforeseen changes to the school timetable. Conclusions: If worn properly, accelerometers can provide an important objective measure of physical activity in population-based studies promoting physical activity. But to achieve generalizable results, it is important to maximize recruitment, retention and adherence to protocol across the study population. For adolescents, adherence may be improved by the following: a ‘two-part’ reward (part one for returns, part two for adherence), personal activity graphs, and less obtrusive belts and monitors.