Cardio Timing
The most fundamental thing to remember about your abs is that you will not be able to see them while that layer of fat is covering them. Thirty to 45 minutes of cardio three to four times a week is a great start. Obviously if you do more cardio the results will come quicker, but not in the form of more cardio per session, but more days. So optimally I would say five to six days a week for 45 minutes, keeping your heart rate in the 130–140 beats per minute range.
