Validation of a widely used heart rate monitor to track steps in older adults.

BACKGROUND

Activity tracking devices gain popularity in research, which is due to their multiple features (e.g. heart rate monitor, step count) and easy handling. Nevertheless, many devices used for research are lacking validation of specific features. This study aimed to assess the validity of the Polar M400© activity tracker to count steps in older adults and, therefore, compared it to a previously validated pedometer (Omron Walking Style©) and observed step count.

METHODS

Thirty-two older adults (mean age: 74.8±5.9 years) walked at a self-selected, normal gait speed on a tartan track for 200 meters while wearing the activity tracker and the pedometer. Additionally, steps were counted manually. Data was analysed using Kruskal-Wallis test and Lin's concordance coefficient. Furthermore, Bland Altman plots were employed to evaluate accuracy of the activity tracker.

RESULTS

Kruskal-Wallis test revealed significant differences between the step count of the activity tracker and the pedometer (P=0.011) but no further differences were observed. Lin's concordance showed a moderate correlation between activity tracker and pedometer (rc=0.561) and between pedometer and observed step count (rc=0.690). A high correlation was detected between activity tracker and observed step count (rc=0.802). Bland Altman plots revealed good accuracy of the activity tracker.

CONCLUSIONS

The Polar M400© activity tracker accurately assesses steps during walking in older adults. Nevertheless, a slight overestimation compared to the pedometer was observed, which should be considered when using the activity tracker for tracking steps over a longer period of time.