Cardio has an important place in a training program but far too many people spend hours on treadmills with little to show for their efforts. Cardio is a less efficient way to burn calories than weight training and, while it boosts the metabolism during the process, that boost is ended as soon as the exercise is. Cardio should be implemented at the beginning of a workout as a short warm up, and then again at the end, in the form of intense activity designed to boost your heart rate to within 90% of maximum capacity. Cardio can also be scheduled on a different day to the weight training part of the program.
Flexibility is achieved as part of the resistance training program. Dynamic stretching is incorporated as part of the warm up and the stretching between sets allows for muscles that are being stressed in a particular exercise to be moved dynamically in the opposite direction.