you breath during aerobic exercises which means that they go on for an extended period of time which is the best way to burn fat. running, bicycling, swimming are aerobic exercises. anaerobic exercises are shorter and you don't really breath during them. sprinting (short distance), and weight lifting are anaerobic exercises

OK, I've answered this a few times bfefore. So I'll give a briefer answer this time. Prolonged aerobic exercise causes you to swtich from burning carbohydrates to burning fats. This occurs after about 20 mins of continous aerobic exercise, though this varies from person to person. It is also easier to burn fat if you are not exercising so sternuously that you find it very hard to breath, because in order to burn fat the molecules have to be converted using oxygen. In general you should exercise at a rate that you can maintain for a long period of time, that you can still talk if you had to but wouldn't really want to. therefore, if you have to choose between 3 sessions of 1 hour and 5 sessions of 40 mins, you will burn more fat following the longer three sessions. Anaerobic exercise does not burn any fat at all, it simply exhausts the glycogen stores in the muscles, an instant but small source of energy for instant movement. No oxygen is used in the metabolism, hence anaerobic. In fact if you notice 100m sprinters on TV, they often don't breathe for the 10 secs or so. Afterwards there is an oxygen debt to repay to help remove the buildup of lactic acid, that causes the 'burn' you fell afterwards, hence the heavy breathing afterwards. Because the glycogen store is a relatively small store, this is why anaerobic exercsie cannot be maintained for long periods of time - you cannot sprint for 2 miles! Personally I choose rowing, because it uses nearly all the muscle groups, as opposed to running/cycling, helping to increase lean muscle mass, which burns more fat at rest. It is also aerobic, and so helps to lose fat.

he he I was going to answer this question but the first answer says it all! spot on! My opinion though I think jogging/running is the best exercise as i think it burns the most fat overall because most people can sustain the duration as opposed to the rower machine ie less tiring on your body. But awesome answer by the way... you know your stuff!