Far too few Americans meet the minimum recommended level of physical activity, an important component of a healthy lifestyle. This dissertation explores the motivational potential of social media as a tool in the development and maintenance of healthy exercise behaviors. The three studies contained herein develop and validate an instrument to measure exercise self-presentation in social media, the SPEQ-SM; use the instrument to assess self-presentation among a sample of exercisers; and explore the relationship between self-presentation, as measured by the instrument, and exercise behavior, using cross-sectional data. Interviews with CrossFit athletes and coaches, along with content analysis of social media profiles and fitness websites, were conducted to determine the types of exercise-related content that individuals generate and consume, as well as their motivations for creating and engaging with such content. The findings of these initial inquiries were leveraged to create surveys, administered online to samples consisting of men and women ages 18-45, most of whom were regular exercisers. Participants answered questions about their social media use, including posting and interacting with fitness-related content; their exercise behavior; their identity as an exerciser; and other psychographic characteristics. The SPEQ-SM was determined to be a good measure of exercise self-presentation in the social media environment, with convergent, discriminant, and nomological validity of the instrument and its two subscales, impression motivation (IM) and impression construction (IC), adequately demonstrated through correlational and factor analyses. The sentiments, beliefs, and behaviors measured by the SPEQ-SM were found to be prevalent in the sample of exercisers. A small but statistically significant relationship emerged between impression construction and exercise volume, and between impression motivation and exercise intensity, both of which appeared to be mediated by identity. Causal claims cannot be made due to the cross-sectional nature of the data; however, this dissertation lays some initial groundwork for future research into the motivational potential of social media-based presentation of the self as exerciser in order to drive healthy exercise behavior
