F45 New York Training is a 45 HIIT workout that will challenge you like never before. The F stands for functional training, a mix of circuit and HIIT-style workouts geared towards everyday movement. 45 is the total amount of time for sweat-dripping and heart-pumping fun. With thousands of exercises in our database and a nearly infinite amount of combinations, members will almost never take the same class twice. F45 Training is here to bring you the world's most innovative workout.