The age requirement to join Bally Total Fitness typically states that individuals must be at least eighteen years old to sign a membership agreement independently. However, it is important to note that some locations may allow minors, those aged thirteen to seventeen, to join with the permission of a parent or legal guardian. In such cases, the parent or guardian often needs to co-sign the membership agreement. Additionally, Bally Total Fitness may have specific policies regarding the use of facilities and participation in classes for younger members. It is advisable for prospective members to explore the current policies and requirements on the Bally Total Fitness website, as these details may vary by location and are subject to change.