Abstract

The aim of the present study was: to compare the validity of assessments, by using uni-axial and tri-axial accelerometry at different physical activity intensity levels (PAL) for monitoring of physical activity at stadium and free living conditions. Activities were divided into three PAL as slow walk, brisk walk and jogging. All activities were performed at stadium and at the forest at cross-country place. Participants of the study performed the tasks at self selected speeds. Pulse monitor “Polar-S810” was used for the heart rate monitoring and a device with the tri-axial accelerometer was attached to the trunk as to measure and calculate the sum of the rectified and integrated acceleration curves from the anteroposterior, mediolateral and vertical directions. The integration period was set at 10 s and the final output was expressed as integrated physical activity level in the vertical axis (ay) and integrated physical activity level of all three axes (ax, ay, az). The integrated values of PAL obtained during the various intensities were normalized for each participants of the study while a level of integrated curves during a slow walk was accepted as one. Analysis of changes in HR during the performance of locomotion of various intensities shoved that the same physical task requires a various energy costs in dependence on the environmental conditions. Cross-country conditions, i.e. mountain and more twists required the more mobilization of cardiovascular system as to perform the task and the bigger changes in HR was observed. The uni-axial accelerometry llowed to identify physical activity across the various intensities investigated at the stadium and at the cross-country conditions. The tri-axial accelerometry more precisely than uni-axial accelerometry allows to measure changes in intensities of physical activity under free-living conditions. Verf.-Referat