Opinion piece
A hitchhiker's guide to assessing young people's physical activity: Deciding what method to use

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Abstract

Researchers and practitioners interested in assessing physical activity in children are often faced with the dilemma of what instrument to use. While there is a plethora of physical activity instruments to choose from, there is currently no guide regarding the suitability of common assessment instruments. The purpose of this paper is to provide a user's guide for selecting physical activity assessment instruments appropriate for use with children and adolescents. While recommendations regarding specific instruments are not provided, the guide offers information about key attributes and considerations for the use of eight physical activity assessment approaches: heart rate monitoring; accelerometry; pedometry; direct observation; self-report; parent report; teacher report; and diaries/logs. Attributes of instruments and other factors to be considered in the selection of assessment instruments include: population (age); sample size; respondent burden; method/delivery mode; assessment time frame; physical activity information required (data output); data management; measurement error; cost (instrument and administration) and other limitations. A decision flow chart has been developed to assist researchers and practitioners to select an appropriate method of assessing physical activity. Five real-life scenarios are presented to illustrate this process in light of key instrument attributes. It is important that researchers, practitioners and policy makers understand the strengths and limitations of different methods of assessing physical activity, and are guided on selection of the most appropriate instrument/s to suit their needs.

Introduction

There is evidence that regular physical activity among young people is beneficial for a range of health outcomes, including improved blood lipid profiles, blood pressure, body composition, glucose metabolism, bone strength and psychological health.1 Physical activity consists of several dimensions including: duration (units of time); frequency (number of sessions, bouts or days); intensity—commonly expressed as metabolic equivalent multiples of resting metabolic rate or METS (light = 1.8–2.9, moderate = 3.0–5.9, vigorous ≥6.0); mode (the type of physical activity behaviour, e.g., bicycling, walking, football); and domain (the context or reason for the physical activity, e.g., household chores, transport, leisure, physical education, occupation).

Young children's physical activity differs substantially from that of adults.2 An observational study reported that children aged 6–10 years had a median bout time of 6 s in light-to-moderate intensity physical activity and 3 s in vigorous-intensity physical activity.3 Interestingly, 95% of children spent not more than four continuous minutes at rest, illustrating the transitory nature of young children's physical activity. In addition, young children are more likely to engage in different types of physical activity (e.g., active play) than their older counterparts.4 Adolescents’ physical activity is also likely to differ from adults’ physical activity. For example, in some countries, by necessity, adolescents may engage in higher levels of active transport (e.g., walking or cycling) as they cannot drive a car. Physical education and physical activity opportunities at school also differentiate adolescent from adult physical activity.

Accurate assessment of physical activity among young people is important for many reasons: detecting positive and negative health outcomes associated with this behaviour; estimating population prevalence and trends; identifying correlates; detecting natural changes over time; and evaluating the efficacy of interventions to alter physical activity. However, choosing the most appropriate instrument depends not only on the validity and reliability of the measure, but also on what the instrument is measuring, how it manages to meet the intended purpose of the assessment, what resources are needed and the population group of interest. There are several useful published reviews that describe the accuracy and reliability of specific instruments for use among children and adolescents.2, 5, 6, 7, 8, 9, 10 On the whole, these reviews recommend the use of instruments that enable the assessment of the sporadic and intermittent nature of children's physical activity and that capture most dimensions of physical activity.

Although most of the published reviews have identified age-appropriate physical activity assessment instruments, a limitation has been the failure to provide a guide as to the suitability of assessment instruments according to study circumstances. A common question facing physical activity researchers, practitioners and policy makers is ‘what instrument should I use?’ However, the answer is dependent upon a range of factors including the purpose of the assessment, target group, research question, resources available, time frame and context. Therefore, the purpose of this paper is to provide a user's guide for those interested in the assessment of physical activity among children or adolescents. We present several real-life scenarios that researchers, practitioners and policy makers may face, provide information on the strengths and weaknesses of different approaches, and suggest the use of a decision flow chart to help with the selection of an appropriate method to assess physical activity.

Section snippets

Selecting a method for assessing physical activity

In April 2007, members of The Australian Child and Adolescent Obesity Research Network (ACAORN) Measurement of Physical Activity and Sedentary Behaviours Special Interest Group (http://www.acaorn.med.usyd.edu.au/) met to develop a guide for researchers and health professionals interested in measuring physical activity in children and adolescents. This guide is confined to young people of pre-school and school age, and to instruments typically used ‘in the field’ rather than laboratory measures

Scenarios

The following scenarios have been selected to represent a range of circumstances in which physical activity data are collected. In working through each case, the reader is encouraged to refer to Fig. 1 and Table 1, Table 2 for the details used to make the most appropriate choice of instrument(s). It should be noted that the information provided in each scenario is only sufficient to recommend the adoption of the type of instrument (e.g., self-report questionnaire), but final decisions about

Concluding remarks

Some risk factors for disease, such as smoking, are relatively easy to measure, as they are somewhat monochromatic behaviours. Daily physical activity, particularly among young people, is a complex blend of events, structured and unstructured, planned and incidental, solitary and social, and which occur for competition, leisure, work, educational, or transportation purposes, at school or at home. No single, currently available assessment tool captures and describes every physical activity

Practical Implications

The success of research into physical activity behaviours depends on the correct choice of measurement approach. This paper should assist researchers and practitioners to make appropriate choices based on the purpose of the research, sample characteristics and practical limitations.

Acknowledgements

Lauren Puglisi provided support with manuscript preparation and Philip Morgan provided helpful feedback on a prior draft. Preparation of this guide was funded by The Australian Child and Adolescent Obesity Research Network (ACAORN). Jo Salmon is supported by a National Heart Foundation of Australia Career Development Award. Anna Timperio is supported by a Public Health Research Fellowship from the Victorian Health Promotion Foundation.

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