America Walks is an observational research study to determine walking behavior of individuals in the United States. The entire study will be conducted virtually by requiring participants to download a mobile phone application (App), The App will leverage the mobile phone's step count sensor technology to automatically determine participants' daily walking activity. Participation is voluntary. Participants can choose not to participate or choose to participate and then stop participating. Participants decision will not result in any penalty or loss of benefits to which they are entitled.

This will be the first study to measure walking activity using mobile phones. It is well known that physical activity can promote well-being and help prevent several chronic diseases. It is recommended that an individual should do moderate to vigorous walking for 30 minutes or walk approximately 10,000 steps everyday. Several studies have reported measuring walking activity using self-reported surveys, or pedometers in samples ranging from a dozen to a couple of thousand participants. However these studies have largely required participants to enter their walking data manually, either from memory or from pedometer recordings.

With the rapid availability of activity sensors embedded in smart-phones (such as Apple's iPhone version 5S and up and several Google's Android phone models), it is now possible to track physical activity data passively from the end-user and do so for longer durations as individuals have increasingly begun to use their Phones as a continuous device of use.

Inclusion Criteria:

• Be at-least 18 years old (self -reported)
• Must reside in the United States (50 states and the District of Columbia); this will be self reported by the participant by entering a zip code which will be checked for valid US zip codes.

Exclusion Criteria:

• Does not have a device that supports Apple HealthKit (iPhone 5s or above) or doesn't not have an Android phone with step count sensors

The study population will be residents of the United States with smart phone

All study data will be released on http://trialx.com/americawalksstudy in aggregate manner and findings will submitted for publication in academic journals such as the Journal of American Medical Informatics. Any identifiable participant information will not be revealed publicly in any manner whatsoever.