Step count accuracy of the Life Plus connected watch at different localizations and speeds in healthy adults, patients with cardiovascular disease and patients with peripheral artery disease: a step count validation study in laboratory settings (Preprint)

Abstract

Smartwatches are increasingly used to monitor and motivate physical activity. Cardiovascular disease patients and peripheral artery disease patients often do not meet national physical activity recommendations. They may, thus, benefit from a physical activity program using smartwatches. The Life Plus smartwatch is designed to facilitate activity monitoring by counting steps, but its validity needs to be determined, particularly in patients who may not have a normal gait, such as those with cardiovascular pathology.

This study evaluates the accuracy of the Life Plus smartwatch (versions 2 and 3) in healthy subjects, cardiovascular disease patients and peripheral artery disease patients at different walking speeds (1.8, 2.5, 3.2, and 4 km/h) and different localizations (wrists, hips and ankles) to determine best accuracy.

Thirty-four participants, comprising of healthy individuals (n=10), patients with cardiovascular disease (CVD) (n=14), and patients with peripheral artery disease (PAD) (n=10), wore 6 Life Plus watches simultaneously (3 of version 2 (V2) and 3 of version 3 (V3)), located on wrists, hips and ankles. Participants walked on a treadmill for 3-minutes sessions at speeds of 1.8, 2.5, 3.2, and 4 km/h, they then performed a 10-minute free walking on the ground and again 3-minutes walking sessions on treadmill at the same speeds. Actual step counts were recorded through video footage.

When worn at the wrist, no significant difference between actual number of steps and step count by V2 watches were found in each group independently (healthy group: P=.25; CVD group: P=.50; PAD group: P=.37). Significant differences were found with the V2 watches at the wrist in healthy group at 3.2 (-5.26%) and 4km/h (-6/13%) (P<.05); in CVD group at 2.5 (-5.94%), 3.2(-13.1%) and 4 km/h (-13.96) (P>.05). When worn at the wrist, no significant difference between actual number of steps and step count by V3 watches were found in the healthy group and the PAD group (healthy group: P=.02); PAD group: P=.90). Significant differences were found with the V2 watches at the wrist in CVD group at 3.2 (-6.43%) and 4 km/h (-7.3%) (P>.05) and in PAD group at 4 km/h (-5.77%) (P<.05).

For optimized counting when worn at the wrist, healthy individuals should prefer V2 watches for slow walking (1.8 and 2.5 km/h) and V3 for higher speeds (3.2 and 4 km/h). Patients (CVD and PAD) should prefer V2 watches at 1.8 km/h and V3 watches for higher speeds (2.5, 3.2 and 4 km/h).

This study was not registered in clinical trials but was approved by the ethics committee of the University Hospital of Saint-Etienne in June 2022 (reference CE 2022-36).