Correlations between the step activity monitor and the DynaPort ADL-monitor

Objective. This study was performed to evaluate correlations between the DynaPort activity of daily living monitor and the step activity monitor. Design. Experimental study with repeated measures. Background. Physical activity becomes more important to assess quality of life, e.g. after clinical interventions such as joint replacement surgery. Methods. Nine subjects wore both devices simultaneously for two days. Limitations and technical problems caused by the devices were assessed by a questionnaire. Correlation coefficients were calculated between parameters derived from both instruments. Results. Only small limitations and problems were reported. Significant correlations were found between the number of steps (step activity monitor) and the percentage of locomotion (DynaPort) (r = 0.95), between the number of steps and the physical activity index (DynaPort) (r = 0.71) and between the physical activity index and the percentage of locomotion (r = 0.76). Wilcoxon-tests between the first and second measurement of each subject did not reveal significant differences but correlation coefficients were poor (r = 0.16-0.36). Conclusions. After one day of simultaneously wearing both devices, the percentage of locomotion can be obtained using only the step activity monitor for additional days. Poor correlations between the first and the second measurements of each subject underline the necessity to record further days to acquire the level of human physical activity.