The purpose of this study is to determine whether a Twitter-based intervention with a private, online support group can significantly increase number of walking steps compared to self-monitoring of physical activity alone or a control group in sedentary women at a women's heart clinic.

Sedentary behavior is a risk factor for heart disease, independent of meeting physical activity guidelines. Tweet4Wellness is an innovative light physical activity, specifically walking, intervention which randomly assigns participants to a 25-person private, online support group that will receive daily, theory-based messages as peer-to-peer discussion prompts. Many text-based interventions do not base the intervention text messages in behavior change theory, but this study will base the daily messages in the behavior change theories such as implementation intentions, social support, mindfulness, and social learning theory.

The trial will be conducted over a 6-month periods. For the first 3 months, there will be 2 groups: Group 1 will receive the Twitter intervention and a "Fitbit" triaxial pedometer to track their steps throughout the day; Group 2 will receive the Fitbit pedometer only.

For the second 3 months: Group 1 an Group 2 will track their physical activity with Fitbit only.

Inclusion Criteria:

• Are a woman
• Are over 18 years of age
• Are English speaking
• Have or are willing to purchase a mobile phone with a camera
• Have or are willing to purchase an unlimited text plan
• Are willing to participate in daily tweets or texts for up to 3 months
• Have an active email account
• Have internet access on your mobile phone
• Use or are familiar with Facebook, Twitter, or other social media
• Text at least weekly

Exclusion Criteria:

• Have certain symptoms or conditions that would not be conducive to increasing your physical activity as determined by your physician
• Are planning on becoming pregnant in the next 8 months
• If our screening survey indicates that you are already adequately physically active
• Do not provide all required personal contact information