Crown of Gamma (2015)

Brothers Romulus and Attila discover a time capsule in their backyard - its sole content is a VHS recording of a 1980s fitness instructor named Abraham. Their sister, Darla, becomes enthralled with The Instructor's program; she starts watching it religiously. Attila, jealous for Darla's love, rivals The Instructor by forming his own fitness cult. However, there is only one for Darla.