The inclinometer function of the AG classifies time as sitting, lying and upright.
In contrast to the inclinometer function, the discrimination of static and active time based on the cut point of 100 counts on the vertical axis was good.
In the laboratory measurement, we assessed the intensity measure and the inclinometer function to discriminate postures of the three activity monitors.
The ICC of the inclinometer function of the AG was 0.59 (CI: 0.22 – 0.81), upright time was systematically higher and sitting time was systematically lower than in the diaries.
The inclinometer function of the AG showed limited validity and a dependence on location of application (hip vs. back) [ 13, 18].
The current study shows that the AP and CAM are able to classify posture and that the inclinometer function of the AG provides no valid posture classification.
Although the AG manual states that the inclinometer function performs best when the AG is worn at the hip area, our findings are in line with the results of McMahon and colleagues who evaluated the validity of the inclinometer function when attached at back, waist and upper leg.
Besides the inclinometer function, the AG also discriminates between static posture (lying, sitting and standing) and activity based on a cut point of 100 counts on the vertical axis.
Although several validation studies of the inclinometer function of the earlier manufactured uniaxial AP showed good posture classification [ 14, 15, 19– 21], we are not aware of a study aimed at the validity of the posture classification function of the triaxial AP.
However, the confidence interval of the ICC of the AG inclinometer function was wide, limiting generalizability to the population level.
