Opinion piece
Objective monitoring of physical activity in children: considerations for instrument selection

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Abstract

There has been a rapid recent increase in both the number and type of objective physical activity (PA) assessment instruments which are commercially available to researchers, practitioners, and consumers. Although this has provided improved capacity for PA assessment, it also presents a somewhat bewildering range of options related to instrument selection for users of these technologies. The purpose of this review is to provide a primer to guide selection of instruments for the objective monitoring of children's PA. In an effort to inform without overwhelming, it is not intended to be exhaustive in terms of all available instruments. A general overview is provided of two primary categories of objective monitors: pedometers and accelerometers. Within each category we focus on distinctly relevant options and features important to consider during instrument selection. In general, the desired outcome measure will determine the specific instrument category, options, and features from which the ultimate instrument choice is made. Other considerations include evidence of validity and reliability, cost, computer interface and download options, memory capacity, data aggregation and storage methods, and general participant and researcher burden associated with instrument use. There is no single objective PA assessment instrument that is appropriate for all situations, populations, and research questions. Further, we can anticipate that the commercial nature of these instruments will drive an even greater range of features and options in the future, increasing both the opportunity and the challenge for objectively assessing PA in children.

Introduction

Over the past 20 years, improved awareness of the health benefits of physical activity (PA)17 has pressured development, validation, and application of new tools to objectively monitor this behaviour for the purpose of surveillance, intervention, or program evaluation. As a result, there has been a rapid increase in both the number and type of objective PA assessment instruments, including pedometers and accelerometers, which are commercially available to researchers, practitioners, and consumers.5, 19 The end users of these technologies can be overwhelmed and confused when attempting to select from the array of instruments, options, and features offered. Instrument selection is further complicated for those who study children's PA due to: (1) the challenge associated with detecting the typically short and sporadic nature of children's PA patterns1; (2) the diversity of developmental maturity/age among potential participants (i.e., from infants and toddlers to adolescents); and, (3) children's inherent curiosity regarding wearable technologies and the associated potential for reactivity to monitoring. As a result, researchers and practitioners scramble to make, at times, under-informed choices with regard to instrument selection.

Therefore, the purpose of this review is to provide a primer to guide selection of instruments for the objective monitoring of children's PA. In an effort to inform without overwhelming, it is not intended to be exhaustive in terms of all available instruments. We begin with an overview of the two primary categories of objective monitors: pedometers and accelerometers. Within each category we focus on distinctly relevant options and features important to consider during instrument selection. Table 1 summarises the primary instrument categories, options, and features covered herein. Finally, we discuss both participant and researcher burdens associated with objective PA assessment, specifically as it pertains to children.

Section snippets

Pedometers

As a category of objective PA assessment instruments, pedometers offer a typically simple and low cost estimate of total volume of PA which is outputted as the number of steps taken. The majority of pedometer instruments currently available detect steps by using a horizontal, spring-suspended lever arm which moves up and down with vertical accelerations of the hip.3 An event (i.e., step) is recorded when a sufficiently forceful (i.e., above the sensitivity threshold of the specific pedometer)

Accelerometers

As noted above, many PA research questions and behaviour change goals may only require a simple indicator of total volume of daily PA participation, an output available from a standard pedometer. However, other questions or goals may be related to more specific components of PA such as the frequency, intensity and duration of daily PA. Intensity and duration of PA are of particular interest within surveillance research24 due to their relationship to current PA public health guidelines.17 A wide

Participant and researcher burden

Participant burden during objective PA assessment is comprised of two primary factors: (1) ease and comfort of instrument wear, and (2) data recording requirements. With regard to the wearing issues, the majority of instruments (including most pedometers and many simple accelerometers) are mounted at the waist, are mostly unobtrusive, and cause relatively minimal participant burden or discomfort. Most waist-mounted pedometers and some accelerometers have pre-molded or manufactured plastic or

Summary

The rapid increase in both the number and type of objective PA assessment instruments has provided improved capacity for PA assessment and increased options for instrument selection for users of these technologies. However, it also presents a sometimes confusing array of options with regard to instrument selection for research and applied uses of PA assessment instruments. Perhaps the most important factor with regards to instrument selection is a researcher or practitioner's required or

Practical implications

  • This review provides an overview of two categories of objective physical activity assessment instruments commonly used in children: pedometers and accelerometers.

  • Options and features important to consider prior to instrument selection for children's physical activity assessment are discussed, providing a primer to guide researchers and practitioners in selection of instruments.

Disclosure statement

The information contained within this review does not constitute an endorsement or recommendation on the behalf of the authors, of any product, manufacturer, or distributor discussed herein. Authors have no financial or other interest in the products or distributors of the products reviewed. This work was not supported by any form of external financial support.

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