Killer Workout

Killer Workout (originally titled Aerobicide) is a 1987 American slasher film written and directed by David A. Prior, and starring Marcia Karr, David James Campbell, Fritz Matthews, Ted Prior, Teresa Van der Woude, and Richard Bravo. The story revolves around a Los Angeles fitness club owned by Rhonda Johnson, whose twin sister burned in a tanning salon five years ago. Detective Morgan begins to investigate the gym, after several of its members are brutally murdered by an unknown attacker.