Mean amplitude deviation calculated from raw acceleration data: a novel method for classifying the intensity of adolescents’ physical activity irrespective of accelerometer brand

Abstract

BackgroundUsing raw acceleration data to assess the intensity of physical activity enables direct comparisons between studies using different accelerometer brands. Mean amplitude deviation (MAD in mg) calculated from resultant tri-axial raw acceleration signal was recently shown to perform best in classifying the intensity of physical activity in adults irrespective of the accelerometer brand. This study compared MAD values and cut-points between two different accelerometers in adolescents.MethodsTwenty voluntary participants (10 girls and 10 boys) of average age of 14 wore two accelerometers (Actigraph GTX3, Pensacola FL, USA and Hookie AM13, Espoo, Finland) and heart rate monitors (M61, Polar Electro Oy, Kempele, Finland) while completing ten 2-min patterns of typical activities ranging from sedentary behaviour to light, moderate and vigorous-intensity locomotion. Bland-Altman method examined the agreement of MAD values between the accelerometers. Correlation coefficient between individual heart rates and MAD values indicated the validity of pattern-based intensity classification. Generalized ordinal logistic regression determined the intensity-specific MAD cut-points for both accelerometers.ResultsMAD values varied from 3 mg (lying supine) to 1609 mg (running). Hookie gave higher values than Actigraph in accelerations exceeding 700 mg. The correlation coefficient between MAD values and heart rates was 0.96 for Hookie and 0.97 for Actigraph. Respectively, the MAD cut-points were 29 and 27 (light), 338 and 330 (moderate), and 604 and 558 (vigorous).ConclusionsMAD values and cut-points of Hookie and Actigraph showed excellent agreement. Analysing raw accelerometer data with MAD values may enable the comparison of accelerometer results between different studies also in adolescents.

Measuring Physical Activity in Free-Living Conditions—Comparison of Three Accelerometry-Based Methods

“…MAD increasingly underestimated LPA but overestimated MVPA compared to Actigraph (significant magnitude-associations in Bland-Altman plots in Figure 3). However, comparable results between the devices might have been achieved if the raw Actigraph data had been analyzed with the universal MAD approach (Aittasalo et al, 2015; Vähä-Ypyä et al, 2015b). However, due to the long-term data collection, raw data were not available for the Actigraph device.…”

“…Mean amplitude deviation (MAD) is a recently proposed universal method to analyse raw triaxial acceleration signals (Aittasalo et al, 2015; Vähä-Ypyä et al, 2015a,b). A strong correlation ( R 2 = 0.94) has been found between incident MAD measured with a waist-worn device (Hookie AM20, Traxmeet, Finland) and oxygen consumption in walking and running (Vähä-Ypyä et al, 2015a).…”

Comparability of published cut‐points for the assessment of physical activity: Implications for data harmonization

“…However, contemporary accelerometers are capable of storing high‐frequency raw accelerations, which are highly comparable between frequently used research‐grade devices (ie, ActiGraph, GENEActiv, and Axivity) . In the last five years, researchers have published open source methods to process raw accelerations in order to obtain alternative acceleration metrics to activity counts . Euclidean norm of raw accelerations −1 g (ENMO) is now widely used and has shown a high agreement between brands, facilitating data harmonization across studies.…”

“…15 In the last five years, researchers have published open source methods to process raw accelerations in order to obtain alternative acceleration metrics to activity counts. 16,17 Euclidean norm of raw accelerations −1 g (ENMO) is now widely used and has shown a high agreement between brands, 15,18 facilitating data harmonization across studies.…”

The ActiGraph counts processing and the assessment of vigorous activity

“…The band-pass filter implemented in the ActiLife counts processing method allows acceleration in a frequency range of 0Á29-1Á66 Hz resulting in an amplitude attenuation of 50% at 0Á25 and 2Á5 Hz. The mean averaged deviation (MAD), Euclidian norm minus one (ENMO) and Activity Index (AI) have been proposed as alternative measures to AG counts not restricting the frequency range (van Hees et al, 2013;Aittasalo et al, 2015;Bai et al, 2016). However, omitting noise reduction or error correction in the acceleration measurements seems to challenge the validity of measuring free-living PA in a noisy environment.…”