The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it 'Jumping Up and Down'.
Rita Rudnor

Cardiovascular exercise, or cardio for short is an indispensible part of the Burn the Fat, Feed the Muscle program. It's any form of exercise that you can do for a decent stretch of time without getting out of breath. It's aerobic exercise, meaning that you burn fat in the presence of oxygen as part of the process. Unfortunately the word 'aerobics' conjures images of women in leotards prancing around to pop music, so cardio is the preferred term.

Cardio tends to be done in one of two modes, steady-state or interval training. In the steady-state mode you work at a more or less constant intensity, with a view to getting your heart rate into a target zone and keeping it there. With interval training you intersperse periods of high intensity where you push really hard with periods of low intensity where you recover. The book has a lot of information about this and also discusses the pros and cons of the various ways in which you can do cardio, e.g. jogging, cycling, etc.

My chosen form of punishment is the rowing machine. As of this week I'm doing 21 minutes and each week I add another minute with a view to getting to 30 minutes eventually. I work in a heart rate zone of 135 to 142 beats per minute, which is about 80% of the maximum heart rate for my age. That's getting on towards the anaerobic threshold, the limit to which you can keep up this type of exercise without getting out of breath.