Optimization of daily physical activity monitoring in adolescents: The use of ActiTrainer accelerometer

Purpose: Limitations in monitoring of physical activity (PA) call for the application of triangulation approaches. The goal of the study is to present a verified triangulation approach to monitor daily PA in adolescents on an example of selected characteristics of PA and to suggest how to interpret the data more accurately.

Methods: The sample consisted of 868 girls and 409 boys (15-17 years old). Daily PA was monitored by ActiTrainer accelerometers (simultaneously monitors PA and heart rate (HR)) and using subjectively reported PA and physical inactivity (PI) daily logs (specifying its duration and type). School days were segmented into periods: Before school, separate lessons, separate recesses, total school time, and after school.

Results: The total daily volume of PA was characterized by 691±241 steps/hour in girls (688±271 boys) and by 0.46±0.20 kcal/ kg/hour (0.52±0.25 boys). Duration of MVPA (≥3METs) was 4.63±2.51 min/hour in girls (5.47±3.02 boys) and duration of MVPA (≥60% HRmax) was 5.58±5.31 min/hour (4.75±5.03 boys). The ratio of PI/PA was 1.75±0.32 in girls (1.73±0.37 boys) which comprised 34.3% (35.2% boys) of the duration of any PA out of the accelerometer wear time. In all the above mentioned characteristics, the volume and intensity of PA was significantly higher (p<0.001) in the before school period as compared to the other periods.

Conclusions: It is reasonable to set minimal and maximal duration of individual monitored segments of a day and to convert the characteristics of PA into a relative values per hour of monitor wear time within the segments.