Review
Methodological considerations in using accelerometers to assess habitual physical activity in children aged 0–5 years

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Abstract

This paper reviews the evidence behind the methodological decisions accelerometer users make when assessing habitual physical activity in children aged 0–5 years. The purpose of the review is to outline an evidence-guided protocol for using accelerometry in young children and to identify gaps in the evidence base where further investigation is required. Studies evaluating accelerometry methodologies in young children were reviewed in two age groups (0–2 years and 3–5 years) to examine: (i) which accelerometer should be used, (ii) where the accelerometer should be placed, (iii) which epoch should be used, (iv) how many days of monitoring are required, (v) how many minutes of monitoring per day are required, (vi) how data should be reduced, (vii) which cut-point definitions for identifying activity intensity should be used, and (viii) which physical activity outcomes should be reported and how. Critique of the available evidence provided a basis for the development of a recommended users protocol in 3–5-year olds, although several issues require further research. Because of the absence of methodological studies in children under 3 years, a protocol for the use of accelerometers in this age range could not be specified. Formative studies examining the utility, feasibility and validity of accelerometer-based physical activity assessments are required in children under 3 years of age. Recommendations for further research are outlined, based on the above findings, which, if undertaken, will enhance the accuracy of accelerometer-based assessments of habitual physical activity in young children.

Introduction

Objective measurement of habitual physical activity via accelerometry is becoming more common in paediatric populations where indirect methods such as self- and parent-proxy reports have a tendency to overestimate activity levels. Accelerometry has provided important insights into the lives of young children, enhancing our understanding of the patterns of physical activity and sedentary behaviour,1 the influence of physical activity on health outcomes such as obesity2 and skeletal health,3 the correlates of physical activity4 and the efficacy of interventions designed to influence physical activity.5 However, researchers using accelerometers to assess physical activity in young children are faced with many methodological decisions when applying this technology and published studies report a wide variety of protocols,6, 7 making such methodological decisions difficult. The purpose of this paper is to review and critique the evidence evaluating different accelerometer methodologies used in young children (for this paper defined as between 0 and 5 years of age), in order to outline an evidence-guided methodological protocol for use in this age group. The paper will also identify gaps in the protocol where sufficient evidence is currently lacking and provides recommendations for future research that would enhance the strength of the evidence base.

Section snippets

Characterisation of physical activity in young children

Physical activity is often defined as any bodily movement generated by the skeletal muscles that raises energy expenditure above resting values.8, 9 Among children aged 0–5 years, this activity mainly takes the form of basic movements and fundamental movement skills, expressed through reflexes and reactions, unstructured activities such as physical activity play and moving to music and through structured activities such as swimming lessons, and simplified dance and gymnastics movements. The age

What is an accelerometer?

Accelerometers are instruments designed to measure time-varying differences in force or acceleration. When applied to the measurement of physical activity, an accelerometer can assess the magnitude and total volume of movement as a function of time. Most accelerometers used in physical activity assessment operate using piezoelectricity derived from microscopic crystalline structures. In such designs, force created from acceleration causes crystals to become stressed/compressed, which in turn

Methodological considerations in using accelerometers to assess physical activity in young children

An increase in the variety of commercially available accelerometers means that researchers face a daunting task when trying to make their selection. Descriptive characteristics, technical specifications and manufacturer details of 14 accelerometers for use in paediatric physical activity studies have been outlined in thorough reviews.15, 16, 17 Factors that may influence the monitor selection process have also been discussed previously6, 15, 17 and include direct and ongoing costs (e.g.

Evidence-guided protocol for using accelerometers to assess physical activity in young children

Critique of the available evidence on accelerometer methodological issues in children aged 0–5 years has provided a basis for the development of a recommended users protocol in this age group (see Table 2). Because of the absence of methodological studies in children <3 years, a protocol for the use of accelerometers in such children cannot be specified. Therefore, extrapolation from studies in 3–5-year-old children would be recommended, and formative studies examining the utility, feasibility

Recommendations for future research to enhance the use of accelerometers for physical activity assessment in young children

Taking into consideration the available evidence and the gaps in the suggested methodological protocol, recommendations for future research that would assist in strengthening the protocol and assist users of accelerometers in making informed methodological decisions are warranted. Very few accelerometers have been validated in 3–5-year olds and investigations are required to demonstrate the accuracy and reproducibility of current and emerging devices. Preliminary studies exploring the utility,

Conclusion

The appropriate application of accelerometry for the assessment of physical activity requires careful deliberation in order to use the technology to provide accurate assessments of this behaviour. Review and critique of the literature investigating accelerometer methodological issues in young children provided in this paper has led to the development of an evidence-guided protocol for 3–5-year olds that will assist users of accelerometers in the decision-making process. Several areas within

Practical implications

  • Accelerometer users should follow an evidence-guided protocol when applying this technology to assess physical activity behaviour in children.

  • Critique of the literature investigating accelerometer methodological issues in young children has led to the development of an evidence-guided protocol for 3–5-year olds that is likely to evolve as further evidence emerges.

  • Studies testing the utility, feasibility and validity of accelerometry in infants and toddlers will assist paediatric physical

Conflict of interest

There are no potential conflicts of interest that may affect the authors’ ability to provide an unbiased view.

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