Agreement of the activPAL3 and activPAL for characterising posture and stepping in adults and children

• During standardised activities activPAL3 and activPAL generally have good agreement.
• There are lower levels of agreement for standardised jogging activities.
• For adults and young people during ADL activPAL3 records more steps than activPAL.
• In young people there were differences in posture classification (sit/stand) for ADL.

Characterisation of physical activity and sedentary behaviour under free-living conditions is becoming increasingly important in light of growing evidence for the health implications of these behaviours. The integrity of long-term follow-up and the ability to compare outcomes between studies is critically dependent on the agreement of outcomes from successive generations of monitors. This study evaluated the agreement of the activPAL and second generation activPAL3 devices. Agreement was assessed in both adults (median 27.6y IQR 22.6) (n = 20) and young people (median 12.0y IQR 4.1) (n = 8) during standardised and daily living (ADL) test activities. During standardised activities; sedentary duration, upright duration, stepping duration and overall number of steps were all detected within small limits of agreement (≤5%). However, the activPAL characterised more steps during jogging than the activPAL3 (adults +8.36%, young people +6.80%). Also during ADL differences arose due to different posture characterisation in young people and lower step detection in the activPAL than the activPAL3 (adults −20.58%, young people −11.43%). Second-by-second posture analysis demonstrated high levels (>90%) of agreement for all activities between monitors. However, sensitivity (68.7%) and positive predictive value (78.8%) for adult stepping demonstrated disagreement between monitor interpretation of movement patterns during ADL. Agreement between monitor outcomes for standardised activities provides confidence that these outcomes can be considered almost equivalent. However, for characterisation of jogging and smaller movements during ADL, it is likely that significant differences between monitor outcomes will arise.