The goal of the present paper is to propose a model for the study of automatic cognition and affect in exercise. We have chosen a dual-system approach to social information processing to investigate the hypothesis that situated decisions between behavioral alternatives form a functional link between automatic and reflective evaluations and the time spent on exercise. A new questionnaire is introduced to operationalize this link. A reaction-time-based evaluative priming task was used to test participants' automatic evaluations. Affective and cognitive reflective evaluations, as well as exercising time, were requested via self-report. Path analyses suggest that the affective reflective (beta = .71) and the automatic evaluation (beta = .15) independently explain situated decisions, which, in turn (beta = .60) explain time spent on exercise. Our findings highlight the concept of contextualized decisions. They can serve as a starting point from which the so far seldom investigations of automatic cognition and affect in exercise can be integrated with multitudinous results from studies on reflective psychological determinants of health behavior.