Methods
In study 1 (N = 777), young adults completed questionnaires assessing Theory of Planned Behavior variables, past behavior, and planning in relation to exercise and 2 weeks later reported exercise behavior. In study 2 (N = 356), young adults were randomly allocated to complete one of two questionnaires and 2 weeks later reported exercise behavior. Both questionnaires contained similar measures to study 1 (Theory of Planned Behavior variables, past behavior in relation to exercise), but one also contained an exercise planning measure.