I have read a few articles about the duration and intensity of aerobics,most of which were in contradiction.
I heard that interval running for 5 minutes with high speed(on treadmill) burns more FAT than running with normal speed for 30 minutes(for example 8.0).
Is it really true?
Currently I do 20 minutes of treadmill and 20 minutes of cycling. I would appreciate it if you could point me in the right direction.
Yes that is true. I will give you an idea of how you can understand this matter better.
When talking about fitness I always like to give an example that is referring to the human body and a regular car. Think of how much fuel your car is going to consume when you are driving with a slow speed and once you are driving a lot faster. Well it's kind of debatable because it really depends on the gear that you are on whilst driving. So let's say the consumption could be very similar.
However the human body can't switch between different gears and thus the faster that you run the more stressful it will feel on your body(higher blood circulation rate, higher breathing rate, higher heart rate, etc). Thus the body will need more energy in order to keep going. In order to provide additional energy it will burn more calories. Now it really depends on how you have structured your workout regimen and your diet plan. If you did them well the calories will come mainly from fat.
Also here's another idea that I want to give you. Some years ago I was experimenting with running and I maximized my results as it follows - Because you can't sprint all the time you can try sprinting for 2 minute(let's say your maximum period of time is 3 minutes). Then jog for another 2 until your breathing stabilizes, then try sprinting for another 2 minutes and jog for another 2. Why do I suggest this method? Think about the car example again. A car will always consume more fuel in the city then it will on the highway. Because in the city the car will have to stop and start again and again(because of traffic jams, traffic lights, etc). Thus that will be very stressful and cause more fuel consumption. If you combine sprinting with jogging you will recreate the same type of stress on your body making it burn more calories in order to keep up. You should consider that this might feel stressful on your heart as well so in case you are overweight or have heart problems you might want to avoid this.
This is a complex topic.
When you are exercising, you are burning both fat and carbohydrate. If you are exercising easily, the bulk of the energy is coming from fat. As you start exercising harder, you will hit the limit of the energy that can be supplied through fat metabolism, and the extra energy will be supplied by carbohydrate metabolism. If you are working very hard, the majority of the energy comes from carbs.
To answer your specific question - whether 5 minutes at high speed burns more fat than 30 minutes at a lower speed, the answer is "probably not", for a couple of reasons.
First, even if you burnt all fat, that would mean that you would have to be working 6 times as hard to burn the same amount of energy in 5 minutes as in 30. That would be a very big spread in effort; if you are working pretty hard at both durations, it would be rare to work twice as hard on a 5 minute (a more typical ratio is perhaps 30% harder).
Second, the majority of the extra energy you burn at 5 minutes would come from carbohydrate, not fat.
So, if you are looking for burning more calories during a workout, a longer workout will nearly always burn more calories than a short one. If you want to lose weight, you should care about the overall number of calories you burn, not just the fat calories you burn.
However, higher-intensity workouts do burn more calories per minute, and can also burn more fat calories per minute. They will also burn additional calories at a higher rate after the workout is over.
A caution: High intensity workouts are harder on your body, and it's easy to overdo it.
