My recommendation for general cardiovascular health and fitness is to do cardio 30 minutes to 1hr (max) 3 days a week. If you are looking to drop serious pounds or increase cardiovascular capabilities then 5 days a week. Adjust your plan to fit your goal. Cardio does not have to be running or sitting on an elliptical. Cardio can be any activity that is done at challenging intensity with little rest. I knock my cardio out in hot yoga, kayaking/ rowing machine, running, cardio