The TPB, The Subjective Norm and Your Health
The Theory of Planned Behavior (TPB) - Developed in 1985 by University of Massachusetts psychologist Icek Ajzen. It suggests that if you want to change your behavior for the better, you'll be more successful if you attach tangible goal.
The Subjective Norm - The thought that participating in the behavior of those deemed important in your life is most acceptable. If you believe other people (especially those closest to you) are supportive of your behavior (i.e. exercise) you will be more successful continuing the behavior.
Your Health - Is more likely to be improved, in part, by combining the above principles. GPP suggests entering an active event (5k, 10k, half, Dirty Dash, cycling tour, etc.) with friends.