Table 2 Evidence-based answers to common practical questions in paediatric accelerometry
QuestionEvidenceReference cited/ comments
How much monitoring is necessary for stable measures of physical activity and sedentary behaviour?3–7 days desirable43; number of days and hours per day need to be determined for each setting and application
Where should the accelerometer be placed?Right-hip placement evidence-based, alternative placements need justification and greater evidence3 5–9
What activity sampling interval (epoch) should be used?Lack of evidenceSee later in this review; the effect of epoch smaller than is appreciated
Which cut-points(s) should be used to convert accelerometry output to physical activity and sedentary behaviour, and to what extent does it matter?Wide variation in practice; implications of using different cut-points not widely appreciatedSee text; critique of existing evidence and new evidence provided
How should data be reduced and interpreted ?Collection of additional information, eg, parent or child log-sheets helpful. Distinct lack of consistency in practice; greater transparency in methods would be helpful5–9
    Missing data
    Strings of zeros
Are cut-points age dependent?Lack of empirical evidence in childrenNew evidence in present text suggests that cut-points are largely independent of age
Uniaxial measurement in (vertical plane)Theoretical advantage to tri-axial accelerometry. Empirical evidence shows no improvement in accuracy with tri-axial systems5–9
Or bi-axial (two planes)
Or tri-axial accelerometry? (all three planes)?