Laboratory measurement of posture allocation and physical activity in children

The purpose of this study was to validate the combined use of inclinometers and accelerometers to measure body posture and movement in children in a laboratory setting.

We performed two separate experiments. In the first experiment, we tested the hypothesis that four inclinometers (tilt sensors) could be used to capture body posture in children. We observed and recorded body posture in eight healthy children (mean +/- SD; body mass index (BMI), 18 +/- 3 kg x m(-2)) on 2880 occasions and compared these records with the inclinometer data. In the second experiment, the hypothesis was that two inclinometers could be used to determine whether 18 children (BMI, 21 +/- 5 kg x m(-2)) were sedentary. We observed and recorded sedentariness (sitting/lying compared to standing) on 5575 occasions and compared these records with the inclinometer data. In both of these experiments, we also addressed the hypothesis that accelerometer output, when measured at varying velocities, correlated with walking energy expenditure.

In experiment 1, body posture was correctly identified in 2880 out of 2880 inclinometer measurements. In experiment 2, sedentary behavior was correctly identified in 5575 out of 5575 occasions. For the entire group, acceleration and body weight correlated well with energy expenditure (r2 = 0.84).

The inclinometer-accelerometer system that we tested can be used to measure body posture and movement. We can measure sedentary behavior using two inclinometers instead of four inclinometers. This monitoring system may be useful for measuring energy expenditure, body posture, and physical activity in children.