Final answer:
Active duty service members must undergo Periodic Health Assessments (PHAs) annually or when there are changes in their health status, or as identified by commanding officers or medical personnel, in order to maintain their medical readiness for duty.
Step-by-step explanation:
Active duty service members are required to have their Periodic Health Assessments (PHAs) performed on a regular basis in accordance with military regulations. The timing of when the PHAs are conducted can vary, but they are typically conducted annually to ensure that service members are medically ready to perform their duties. They may also be performed when a service member's health status changes or when there is a specific need identified by their commanding officer or medical personnel.
It is part of a service member's duty to maintain their health and fitness for duties as per the obligations laid out in laws such as the Military Service Act, which stipulates the conditions under which individuals are eligible for compulsory military service. Exemptions, including medical exemptions, are provided under special circumstances. Ensuring one's health through a PHA is fundamental to fulfilling the commitment of service made when taking the military oath.