If your looking to burn calories fast then the tred mill is the best way, recently Dublin university researchers looked into the burn ratio on cardio vascular machines. Results found that running is the best method for fitness. How long it takes to burn 200 calories 14 minutes (tred mill)16 minutes (X trainer)21 minutes (rower)29 minutes (bike)The reasons behind this result are simple, when we choose to run on the tred mill we are using more muscles, we also use more body weight when exercising. The other cardio machines support our body weight more, they reduce the amount of weight used in each exercise, meaning less body weight, burn less calories!The ideal way to go about it is to make use of intervals and varying degrees of inclination. The reasoning behind this is that maintaining a constant cadence on a flat surface is not particularly difficult, whereas executing the movement on an incline raises the difficulty sufficiently to maximise the amount of work being done per unit of time.