Force Fitness Instructor (FFI) Trainers demonstrate proper pull-up technique for the class of FFI students before executing practical application as part of their course requirement at Marine Corps Base Quantico. FFIs will be a cornerstone of the new Force Fitness division recently created to oversee all aspects of physical fitness for Marines. - Force Fitness Instructor (FFI) Trainers demonstrate proper pull-up technique for the class of FFI students before executing practical application as part of their course requirement at Marine Corps Base Quantico. FFIs will be a cornerstone of the new Force Fitness division recently created to oversee all aspects of physical fitness for Marines.