Development of a Smartphone Application to Measure Physical Activity Using Sensor-Assisted Self-Report

Abstract

Introduction: Despite the known advantages of objective physical activity monitors (e.g., accelerometers), these devices have high rates of non-wear, which leads to missing data. Objective activity monitors are also unable to capture valuable contextual information about behavior. Adolescents recruited into physical activity surveillance and intervention studies will increasingly have smartphones, which are miniature computers with built-in motion sensors.Methods: This paper describes the design and development of a smartphone application (“app”) called Mobile Teen that combines objective and self-report assessment strategies through (1) sensor-informed context-sensitive ecological momentary assessment (CS-EMA) and (2) sensor-assisted end-of-day recall.Results: The Mobile Teen app uses the mobile phone’s built-in motion sensor to automatically detect likely bouts of phone non-wear, sedentary behavior, and physical activity. The app then uses transitions between these inferred states to trigger CS-EMA self-report surveys measuring the type, purpose, and context of activity in real-time. The end of the day recall component of the Mobile Teen app allows users to interactively review and label their own physical activity data each evening using visual cues from automatically detected major activity transitions from the phone’s built-in motion sensors. Major activity transitions are identified by the app, which cues the user to label that “chunk,” or period, of time using activity categories.Conclusion: Sensor-driven CS-EMA and end-of-day recall smartphone apps can be used to augment physical activity data collected by objective activity monitors, filling in gaps during non-wear bouts and providing additional real-time data on environmental, social, and emotional correlates of behavior. Smartphone apps such as these have potential for affordable deployment in large-scale epidemiological and intervention studies.

A recommended guideline for the development of mHealth Apps

“…There are at least 4 large operating systems for smart devices, drivers that are not standard and protocols that differ between mobile phone producers (1). There is also a variety of programming and design techniques leading to a heterogeneous configuration of the mHealth app development (19). Consequently, the consolidation of all different systems remains a challenge in the developers' field (9).…”

Novel Technologies to Study Smoking Behavior: Current Developments in Ecological Momentary Assessment

“…Participants can use smartphones to take photographs, record videos, or make audio recordings, in addition to traditional self-report information such as diaries, surveys, and event logs. Dunton and colleagues [31] have combined EMA with objective assessments of physical activity making use of the built-in motion sensor in smart phones-a data collection strategy they call context-sensitive momentary assessment (CS-EMA). This is superior to previous research about people's day-to-day physical activity which has relied upon retrospective recall and/or activity monitors, which are not equipped to gather behavioral and contextual details, such as the type of sedentary or physical activity that was being performed, or to link the activities with mood, behaviors, and context.…”

Assessing the Exposome with External Measures: Commentary on the State of the Science and Research Recommendations

“…Data on perceptual information can also be gathered through context-sensitive ecological momentary assessment (CS-EMA) through real-time self-reported smartphone assessments. The system can, for example, request a person to respond to a survey either at random or when particular events are sensed through a smartphone-enabled system, such as the use of steroid inhalants (31), a period of physical activity (29), contact with nature (25), or air pollution exposures. EMA surveys provide rich data on mood, stress, social context, environmental perceptions, or behaviors at the point of contact between the exposure and receptor (30,46).…”