No matter your level of running, doing double 3 or 4 times a week can help you Increase your cardiovascular strength and odd move your metabolism up a notch. It's a simple equation: the more you run, the more efficient your VO2 max. With a higher VO2, you process oxygen more Efficiently, therefore ALLOWING you to use less energy to run faster. Not like any new addition to a training program, must be in double Adding a gradual transition so you save yourself from injury and burnout Both. Start with an added run one day a week for about 2 weeksdepending on how your body reacts, add 2 to double the Following week and Then 3.