The results of prominent meta-analytic reviews suggest that when people exercise in groups they tend to sustain their involvement to a greater extent than when they exercise on their own. Despite the potential for groups to sustain long-term physical activity behaviours, there appears to be an important caveat that comes with exercising with others: if people perceive themselves to be similar to other members of a given group, in terms of salient underlying qualities, this corresponds positively with their attraction to, and level of involvement within, that group. If, however, people perceive themselves to be distinctly different from others within their social group, this is likely to undermine their attraction to, and involvement in that group. Recent research by Dr. Beauchamp and his team suggests that across the adult age spectrum people report a positive preference for exercising within groups that are comprised of others their own age, and when they participate in such classes they display higher levels of adherence to the group. In a similar regard, people report comparable positive preferences for same-gender rather than mixed-gender physical activity group settings. However, to date, research has yet to examine these effects using an experimental (RCT) design. This constitutes the purpose of this present trial.