Stiftung Warentest
Certain movements of the user, such as working in the household, cycling, swimming, dancing or rowing can distort the results obtained from activity trackers. In a test conducted by Stiftung Warentest, for example, no product determined the distance of a bike ride, even approximately. Furthermore, the determined values for the human energy transformation were erroneous. With the heart rate large deviations have been observed at wristlet trackers, and it is recommended for this purpose to use appropriate chest straps.