Caroline Kaylor, Grace Lehman, Christopher G. Ballmann, FACSM, Patrick Marsh, Rebecca R. Rogers. Samford University, Birmingham, AL.

BACKGROUND: Previous research has shown varying levels of accuracy of gait metrics from third-party applications (apps) downloaded to a mobile phone compared to lab-based measurement tools. The Apple Health app comes automatically installed on all iPhones with the recent addition of “Mobility” data after a software update. According to Apple, when walking with an iPhone in a pocket, the Mobility feature will measure the gait variables of step length, double support time, walking speed, and walking asymmetry. However, the accuracy of these measurements is unknown. Therefore, the purpose of this study is to investigate the accuracy of the mobility metrics during overground and treadmill walking compared to the OptoGait and GAITRite which have been previously validated for gait variables. METHODS: College-aged males (21.0±0.8 yrs, 196.4±38.2 lbs, 73.0±2.4 in) and females (20.7± 1.3 yrs, 132.4±18.4 lbs, 64.9±2.0 in) who reported no abnormal gait patterns or lower extremity injuries were recruited into the study. The study was approved by the university Institutional Review Board and all participants provided informed consent. Participants completed two walking conditions: overground walking at a self-selected walking speed for five laps using the GAITRite to measure gait variables and treadmill walking at 3.0 mph for 10 mins using the OptoGait to measure gait variables. For both walking conditions, an iPhone 13 was placed in a fanny pack-like pouch and secured to the participants waists in a standardized position at the level of their navel and in line with the midline of their dominant leg to simulate a pocket. RESULTS: The gait variables of step length for overground (p=0.07) or treadmill (p=0.13) walking and walking speed for overground (p=0.27) or treadmill (p=0.16) walking were not significantly different between the iPhone Apple Health Mobility app and the GAITRite or OptoGait. However, iPhone Apple Health Mobility app significantly underestimated total double support time during overground walking with the GAITRITE (p=0.00) and treadmill walking with the OptoGait (p=0.04). Furthermore, walking asymmetry was also significantly underreported by the iPhone Apple Health Mobility app compared to GAITRite (p=0.00) and OptoGait (p=0.00). CONCLUSION: The iPhone Apple Health Mobility app can accurately measure step length and walking speed during different walking conditions but may underestimate the gait variables of double support time and walking asymmetry compared to validated equipment.

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