Welcome to HPA The Catalyst, the Section on Health Policy & Administration of the American Physical Therapy Association (APTA). We're glad you're here. HPA The Catalyst is a professional association for physical therapists, physical therapist assistants, and students. We are a specialty component of the APTA, but a separate association with our own Board of Directors, staff, and location. We serve approximately 2,400 HPA/APTA members with special interests in the areas of leadership, administration and management, global health, and technology in physical therapy.