Physical activity (PA) has been shown to be an important component in preventing a number of negative health outcomes and in improving cardio respiratory fitness. However, there is little consensus as to what mediates the relationship between PA interventions and PA behaviors. Numerous studies have identified self-regulation as a proximal mediator of PA interventions, but there appears to be little consensus as to what constitutes self-regulation and how it should be measured. The current study explores the theoretical underpinnings of self-regulation from several different theories and identifies several measures related to those theories. Overlapping factors are identified by combining the measures and conducting exploratory and confirmatory factor analyses in order to understand the components of self-regulation. The results of the factor analyses revealed a seven-factor model consisting of 96 items. The factors from the final model included Self-Regulation Self-Efficacy, Negative Affect, Goal Setting/Goal Planning, Goal Communications, Goal Setting/Outcome Expectancy, Self-Monitoring, and Goal Planning. Analyses reveal that Goal Setting/Goal Planning and Goal Setting/Outcome Expectancy significantly predicted PA behaviors. How these factors relate to the theories of self-regulation and how they relate to the original measures are discussed; however several factors derived from this study contained several theoretically distinct constructs which made interpretation of these factors difficult. Future directions for identifying and developing factors of self-regulation are discussed and special consideration is given to the process of self-regulation.