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Accelerometer-based devices are now commonly used to characterise physical activity (PA) behaviour in research and consumer applications. In this article, we present several topics related to the growth in use of accelerometers that should be of interest to PA researchers and research consumers. A review of the history of accelerometers in PA research provides the background. This is followed by a discussion of new approaches to analyse acceleration data that are feasible because of technological advances in devices and computing. Two related projects of interest to the PA research community are described: a collaborative effort to harmonise accelerometer data analysis and the collection of accelerometer data in the US National Health and Nutrition Examination Survey (NHANES) 2011-2014. The article concludes with further observations based on our experience with accelerometer-based devices in population monitoring.
Brief history of accelerometer-based PA research
The first accelerometer-based PA monitor to be adopted by researchers was developed in the 1980s, 1 and the 1990s saw a proliferation of new research devices. During these early years, accelerometer-based devices were seen as an intriguing, although niche, assessment technology due to limitations that included high device cost, as well as reliability, calibration and validity concerns. 2 While many of these challenges are still being debated today, by the early 2000s, accelerometer technology was more accessible and the apparent value of objective PA data collected over multiple free-living days had grown attractive to many PA researchers. 3 The application of accelerometers as a measure of PA has expanded exponentially. In 2004, an examination of the number of published articles mentioning PA or exercise and accelerometer or accelerometry found that the publication rate had increased from roughly 10 or fewer per year in 1981-1996 to nearly 90 per year in 2003 and 2004. 3 A recent update of that publication count finds that more than 600 articles per year were published in 2012 and 2013 ( figure 1 ).
The 2004 publication count was conducted for a conference titled 'Objective measurement of physical activity: closing the gaps in the science of accelerometry.' Presentations at the workshop, which were summarised in a supplement to Medicine and Science in Sports and Exercise (Med Sci Sports Exerc 2005 Nov;37 (11 Suppl)), highlighted the developments of the...