The purpose of this research is to test programs to increase physical activity and reduce sedentary behavior using motivational messages over a cell phone.

We want to learn if conceptually-based behavioral interventions for promoting increased physical activity and decreased sedentary behavior via state-of-the-art mobile phones will be efficacious at improving these behaviors relative to commercially available Android applications as a control. If efficacious, these types of intervention programs could be disseminated to a wide variety of sedentary and underactive adults at a relatively low cost. This could have a potentially significant impact on promoting improved health such as reduced obesity, a key problem within the U.S.

Inclusion Criteria:

• aged 45 and older, currently sedentary, owns and uses a cell phone but not a Smartphone, willing to be randomly assigned

Exclusion Criteria:

• free of clinically evident cardiovascular disease or any other medical condition or disorder that would limit participation in moderate intensity physical activities akin to brisk walking