Community based interventions are more acceptable to community members when all participants receive the intervention. A 'stepped-wedge' or 'multiple-baseline' design allows for all participants to receive the intervention by randomizing participants into conditions defined by the length of the baseline period. The primary aim of this pilot study is to gather data that will allow the researchers to estimate parameters, such as the appropriate length of the baseline period that will allow them to power a larger study. A second key aim is to determine if a smartphone intervention that is delivered to parents can increase physical activity in their 6-10 year old inactive children.

Low levels of physical activity in childhood are related to obesity and risk for diabetes and cardiovascular disease. This translational study is an attempt to take interventions that have been shown to be effective in highly controlled setting and implement them in the community. We will utilize a form of a single case design (i.e., stepped-wedge or multiple-baseline design), which is an underused, though promising, alternative to the traditional, parallel-group randomized trial in which each study participant acts as his/her own control. Participants will be randomized to baseline periods of varying length such that the change in the study outcome can be causally attributed to introduction of the intervention. In accordance, families will be randomized to a 2, 4, or 6-week baseline period before being administered the P-Mobile app based intervention. All families will receive the same P-Mobile intervention following the baseline period. The P-Mobile intervention will be delivered to parents via the P-Mobile smartphone app; it consists of 10 lessons designed to increase physical activity in children. The parents will also receive notifications designed to prompt physical activity, motivate, and remind parents of lesson content. The intervention will also utilize an adaptive step goal approach, in which the step goal is modified based on each participant's individual performance. The primary aims of the study are: (1) To estimate several parameters, which will allow us to redesign our study as a single case design (and to conduct simulation-based power calculations): (a) average day-to-day variability in daily steps during the baseline period, (b) average autocorrelation in the daily step data, and (c) average effect size at 2 weeks, 4 weeks, and 6 weeks after introduction of the intervention. (2) To test the feasibility of the P-Mobile app (3) To demonstrate our ability to recruit participants from targeted neighborhoods.

Inclusion Criteria:

The child must:

• Be 6-10 years of age
• Have at least one participating parent.
• Be Physically capable of exercise
• Have an average steps/day less than the 50th percentile for age and gender (e.g., <8,900 steps/day for 10-year old girls and <10,200 steps/day for 10-year old boys).

The parent must:

• Have a smartphone
• Be willing to download and use the P-Mobile app
• Demonstrate the ability to send text messages
• Have no plans to move during the study period (up to 4 months)

Families must:

•Reside in targeted geographic area

Exclusion Criteria:

Exclusion criteria for the child includes:

• Significant cardiovascular disease or disorders via self-report
• Other significant medical problems that would prevent them from engaging in regular physical activity.