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 allowed 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.

The general purpose of this study was to present a newly developed system designed for monitoring of cardiovascular and physical activity changes. The hardware system consists of the device for registration of ECG and accelerometers signals and wireless transmission to computer. The coach software works in two modes: on-line version is used during training and offline version is designed for detailed data analysis after training. Subjects performed six different locomotors tasks: 1 – unrestrained walking; 2 – short-step walking; 3 – long-step walking; 4 – unrestrained running; 5 – short-step running; 6 – long-step running along a standardized stadium circuit; and each locomotor activity follow-up for a 180 seconds. The present investigation also confirmed the large inter-individual variation of acceleration while performing the same exercise. The data obtained during the study showed that assessments by accelerometers overestimated intensity of physical activity during short-step walking and running, and underestimated it during the same locomotion performed by long-step. The results obtained during the investigations allows to conclude that developed ECG and motion activity monitoring system with two packages of software allows to measure and asses the cardiovascular and physical activity changes during the walking and running tasks.