Table 1

Description of accelerometer-based descriptors of physical behaviours

DescriptorBrief descriptionExamples
Average acceleration or steps per dayArithmetic average of the processed acceleration throughout the measurement period or per day.29 36 46–48
Time-use behavioursEstimates of time spent in physical activity intensities (eg, LPA, MPA, VPA), types (eg, walking, running, cycling), or SB, optionally expressed in bouted and unbouted behaviour. These estimates can be derived with heuristic methods or ML.29 49–52
Intensity spectrumThe intensity spectrum is an extension of cut-points which attempts to provide a much more detailed description of the physical activity intensity pattern. Instead of using cut-points representative of SB, LPA, MPA or VPA, the cut-points are arbitrarily selected to obtain a wider range of intensity bands.32 33 53
Intensity gradientThe intensity gradient describes the negative curvilinear relationship between physical activity intensity and the time accumulated at that intensity during the 24-hour day.36 46
MX metricsThe acceleration above which a person’s most active X minutes/time (MX) are accumulated, to focus on a person’s most active periods of the day.54 55
Acceleration functionsDescription of the accelerometer data with a function rather than with a scalar. Functions seek a more detailed description of the accelerometer data without making a priori assumptions.38 39 56
Other indicatorsApart from the descriptors related to energy intensity or acceleration levels, an array of metrics can provide complementary information, such as: physical activity domain, circadian rhythmicity, timing, sleep efficiency, etc.34 57 58
  • LPA, light physical activity; ML, machine learning; MPA, moderate physical activity; SB, sedentary behaviour; VPA, vigorous physical activity.