What factors motivate individuals to participate in sport or fitness activities? This question has been of great interest to researchers. However, most studies on motives have considered only a single or a few variables in their investigation. The purpose of this research is to explore the wide range of factors that motivate people to participate in a fitness activity, namely aerobics. To take into account the broad range of individual and social factors that influence participation in a fitness activity, social identity theory is the basis for a qualitative investigation. The findings that show motives for participation are divergent across groups of similar individuals. The motives that emerged were (a) the atmosphere of an aerobics class, (b) the physical and psychological benefits, (c) social ties related to aerobics, (d) social comparisons, (e) obsession with aerobics, and (f) the feelings participants associate with doing aerobics. A proposed framework of fitness participation is developed based on the findings that could serve as a foundation for future empirical studies.