The purpose of this research was to provide a comprehensive descriptive content analysis of empirical research focused on muscularity and published in refereed journals in 2000 through 2019. This is the second part of a two-part series in which the research aims were to characterize the research on muscularity with respect to the theories employed, the measures of muscularity utilized, the extent to which researchers reported reliability and validity for measures of muscularity used, and to report on the journals that publish this type of research and the disciplines these journals represent. We present an overview of relevant theories and how they can be applied to understanding muscularity. This presentation is followed by a discussion of measurements of muscularity. To locate studies multiple available databases were searched resulting in a sample of 176 empirical articles which collectively contained 203 studies. Most studies did not report using theoretical guidance. Of those researchers that did report theories, most used theories from the body image literature; the tripartite model was used most frequently. In 181 studies at least one measure of muscularity was used. The most frequently employed measure was the drive for muscularity scale. A plurality of studies reported their own assessment of reliability as well as others’ reliabilities for the same measure. Most studies did not report validity for muscularity measures employed. Articles analysed came from a wide variety of journals primarily representing two major fields of inquiry: psychology and interdisciplinary.