Google fit smartphone application or Gt3X Actigraph: Which is better for detecting the stepping activity of individuals with stroke? A validity study.

Objective: To examine the validity of the GT3X ^® ActiGraph accelerometer and the Google Fit ^® smartphone application in estimating stepping activity in people with chronic stroke.
Methods: Thirty-seven stroke survivors walked along a straight, 10 metre hallway over 5 min at their fastest speeds, wearing the GT3X ^® ActiGraph accelerometer and a smartphone on their paretic lower limb. The criterion-standard measurement made was the actual number of steps, counted by a trained examiner.
Results: The mean estimated steps measured by the GT3X ^® ActiGraph and Google Fit ^® respectively were 276.7 ± 97.6 and 481.0 ± 119.8; that calculated from the examiner's measurements was 472.0 ± 93.9. Statistically significant associations were found between the actual steps and those estimated by the GT3X ^® ActiGraph (r = 0.56; p < 0.001) and Google Fit ^® (r = 0.89; p < 0.001). The Google Fit ^® application demonstrated the highest reliability coefficient (ICC[2,1] = 0.93; p < 0.001; p = 0.37), compared to that of the GT3X ^® ActiGraph (ICC[2,1] = 0.32; p < 0.001; p < 0.001).
Conclusions: The GT3X ^® ActiGraph underestimated the data and may not be the most appropriate device to estimate the stepping activity of stroke patients. The findings support the validity of a smartphone application in estimating the stepping activity of individuals with stroke, when worn on the paretic side.
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