How Accurately The Smartwatch Measures Steps?

Abstract

Wearable activity trackers are getting popular in the fitness market to track individual’s activity level and several research studies have examined the validity of popular wearable activity trackers. However, there is still limited research regarding the validity of smart watch. PURPOSE: The present study was to systemically examine the validity of the Apple watch for measuring steps. METHODS: Healthy individuals (mean ± SD; age = 23.5 ± 13.4 years; body mass index = 26.8 ± 4.2 kg·m2) participated in the study. The participants were asked to wear the apple watch while normal walking, fast walking and running for one lap on an indoor track (i.e., 200-meter track). The actual steps were manually tallied by researchers using a hand tally counter and the steps on the watch were recorded before and after each test, step counts from the apple watch were compared with manually counted steps. Pearson correlation was calculated to identify the measurement relationship between the counted steps and the recorded steps from the apple watch. Mean absolute percentage error (MAPE) were calculated to examine the measurement error of the Apple watch steps. A dependent t-test was performed to the significant mean differences between counted steps and recorded steps from the apple watch. RESULTS: Total step counts (means ± SD) for counted steps were 222.3±82.5 for normal walking, 198.2±55.7 for fast walking, and 185.9±35.7. Recorded steps from the apple watch were 216.9±77.7 for normal walking, 198.2±55.7 for fast walking, and 188.4±37.9 for running. Pearson correlations were r=.96 (p=.001) for normal walking, r=.83 (p=.000) for fast walking, and r=.93 (p=.000) for running, respectively. Corresponding mean absolute error rates (computed as the average absolute value of the individuals’ errors) were 6.1 ±6.6%, 8.8±11.2%, and 4.3±5.8%, for normal walking, fast walking, and running, respectively. Dependent sample t-tests indicated that there is no significant difference (t(35)=.989, p=.359) between the counted steps and the recorded steps from apple watch. CONCLUSION: The results demonstrate that the apple watch accurately measures steps on normal walking and running conditions compared to the manually counted steps. However, further research is needed to with more sample size and various populations. Words: 1972/2000