From AR 215-1 Chapter 8-20D

Youth use. All participants are expected to conduct themselves in a reasonable, responsible, and prudent manner in accordance with facility rules and regulations. Youth may use adult indoor physical fitness centers only under the following provisions:

1. Service member programs must not be displaced.
2. Children 12 years old and under may not use mechanical cardiovascular equipment, or strength, sauna, or steam rooms or jacuzzi areas at any time.
3. As a Family member, children and youth (15 years old and under), not otherwise prohibited in paragraph 8–20d(2), must be actively participating in the same activity and under the direct supervision of a parent or guardian.
4. Youth must be a participant in a special program, organized and conducted by CYS, schools, or other authorized youth organizations.
5. Children of kindergarten age and older will use gender-appropriate showers, locker rooms, and bathrooms.