F45 Training: Never Heard of It? You Will — and Soon

F45 Training is deceptively simple: the "F" stands for Functional and the 45 for the number of minutes of the workouts from start to finish. The workout is a combination of circuit, HIIT, and heavyweight training with a dash of CrossFit. Like CrossFit boxes, the F45 style is minimalist by design, with white walls emblazoned with the company logo as the only decoration.

The eye candy is the equipment, which is as diverse as the workouts: rowers, stationary bikes, benches and steps, kettlebells and free weights, TRX and battle ropes, BOSUs and medicine balls . . . multiple fitness tools to keep muscles confused and participants engaged.