Activating the core muscles through exercise training programs is believed to be important for athletic performance. Considerable attention has been credited to the lumbar multifidus, transverse abdominis, and quadratus lumborum in designing exercise training programs. Numerous core exercise claims and recommendations abound in the fitness and physical therapy communities touting a superior core challenge for these muscles. The plethora of core activation literature with conflicting outcomes has convoluted the process of choosing exercises for an optimal core training approach. Although an abundance of research studies have quantified the muscle activity, collectively, a consensus on the type of exercise that elicits the largest muscle activity does not exist. Therefore, the objective of this investigation was to critically examine the literature and synthesize the muscle activity produced across various physical fitness exercises to determine which type of exercise elicits the largest amplitude for the core muscles in healthy individuals. PubMed, EMBASE, SPORTdiscus, CINAHL, (CCRT) and Web of Science databases were searched revealing 27 studies meeting the inclusion criteria measuring EMG activity during 202 exercises. In absence of research for the quadratus lumborum, no conclusions could be made and bring about concern for current recommendations. Furthermore, the methodological diversity significantly limited the quality of studies meriting standardization for future EMG research. Nonetheless, the current evidence suggests free weight exercises and non-core exercises using external resistances produce the largest EMG activity for the lumbar multifidus and transverse abdominis, respectively.