Validation of smartphone step count algorithm used in STARFISH smartphone application

Abstract

Step counts of the STARFISH application and the activPAL TM were compared at corresponding speeds and Bland-Altman statistics used to assess level of agreement (LOA). RESULTS:The LOA between the STARFISH application and activPAL TM varied across the four speeds and positions, but improved as speed increased. The LOA ranged from 105-177% at 0.44 m·s -1 ; 50-98% at 0.67 m·s -1 ; 19-67% at 0.9 m·s -1 and 8-53% at 1.33 m·s -1 .The best LOAs were at 1.33 m·s -1 in the shirt pocket (8%) and upper arm strap (12%) positions. CONCLUSIONS:Step counts measured by the STARFISH smartphone application are valid in most body positions especially at walking speeds of 0.9 m·s -1 and above.

Exploring the Feasibility and Usability of Smartphones for Monitoring Physical Activity in Orthopedic Patients: Prospective Observational Study

“…However, the correlation remained relatively high even during the postoperative period ( r =0.64 and r =0.75 for total steps and steps-1, respectively). This discrepancy in the correlation could be attributed to the possibility that patients do not carry their smartphones as frequently during the postoperative period as they would under normal circumstances, or it could be because of the lower measurement accuracy in lower walking velocities, which has been demonstrated in previous studies [ 33 , 34 ]. Regarding the PA tracker’s steps-2 and steps-3, we could not find a significant difference in the correlations between subject groups with different characteristics (the P values were between .06 and .80).…”