A very popular mode of training in recent years has been the use of instability devices and exercises to train the core musculature. Instability training is viewed by many as the most effective way to train the core; however, evidence on this topic paints a slightly different picture. An extensive review of the literature by Behm et al. 2010 (Appl. Physiol. Metab. Nutr. 35(1): 91-108) identified the fact that instability training can increase core muscle activation, but it may not be the best choice in all situations. Unstable training can reduce overall muscular power output, which may have important implications if the goal of a given training program is to maximize the output or physiological stress on a given muscle, as is the case in certain types of athletic training or in certain clinical exercise situations. Nevertheless, the balance of this evidence leads to the recommendations in the position stand (Behm et al. 2010, Appl. Physiol. Metab. Nutr. 35(1): 109-112) that instability training can play an important role as part of an overall periodized program for an athlete, as part of a rehabilitation program in recovery from injury, or as an interesting and novel training mode for the general population in pursuit of musculoskeletal health benefits who may not have access to or want to complete more intensive free-weight training programs. More research is needed to establish the effectiveness of instability training in preventing injury in sports, enhancing on-field sport performance, or for use in various clinical situations outside of rehabilitation for low back pain.