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The Benefits of High Intensity Interval Training (HIIT) for Fat Loss

The Benefits of High Intensity Interval Training (HIIT) for Fat Loss

Friday 17th November 2017
Jonny Carter

High Intensity Interval Training (HIIT) is a popular form of training which involves quick intense bursts of exercise followed by followed by short recovery periods. This type of workout can last any length of time from as little as 4 minutes up to around 30 minutes including rest periods. This means it is time efficient and can be performed anywere including at home. HIIT training gets your heart racing and burns more fat, so how does it do this.....

Firstly I will mention the body gets energy from 3 sources, the macronutrients carbohydrates, fats and in severe cases proteins. These fuel sources are all broken down by the body through different metabolic pathways into the bodies main energy source Adenosine Triphosphate (ATP).

When you use any of the cardio equipment at the gym you are likely to see a 'pretty little graph' on the machine telling you that if your working at around 50-70% of your maximum heart rate (i.e. low-moderate intensity) you are in the 'fat burning zone'. This is very true, as your bodies preferred energy source is fat, this is because the body can store lots of fat and therfore has a large supply of this macronutrient. However the problem with steady-state cardio is yes you will burn fat during the time you are training (e.g. 45 minutes) but as the graph shows, as soon as you finish you will almost immediately slow down fat metabolism.

Interval training is alot more intense than steady-state cardio and therfore will use mainly carbohydrate as fuel intstead of fat this is because although fat provides the body with the most energy it is broken down very slowly into energy and therfore when you are working hard fat is broken down too slowly to be used as fuel for your intense workout. Carbohydrate's metabolic pathway is much quicker, therfore will be used for this type of workout.

So what is the point in using interval training (and getting yourself exhausted) if you burn more fat doing steady-state cardio? Are you just wasting your time and effort?!! NO YOU'RE NOT! Here is the good bit!

High Intensity Interval training increases your body's demand for oxygen, that feeling that you can hardly breathe means your body can't take in enough oxygen to facilitate the activity. This leaves the bodies cells with a massive oxygen debt and like any debt this needs to repaid! This means when you have finished your interval training your body starts trying to repay this oxygen debt. This is called Excess Post-Exercise Oxygen Consumption (EPOC). This metabolic process can last up to 48 hours. This is the 'afterburn' effect (see the graph in the picture). This means your body burns more calories in this period of time as it is needing more energy for the EPOC process. These calories will be burnt as fat as the body doesn't need to rush to complete the process, therefore it will revert back to it's preferred fuel source after the interval session is completed. Therefore what is more benficial 45 minutes of 'fat burning' through steady state cardio or 10 minutes of high intensity interval training, followed by up to 48 hours of increased 'fat burn'?! Pretty obvious really isn't it?! High Intensity Interval Training all the way!

Now the added benefit of certain exercises is that coupled with the high intensity cardio workout it gives you, it also is a resistance workout as you perform bodyweight resistance exercises e.g. squat jumps, tuck jumps, press ups etc, using the large muscle groups. This will cause muscle fibre tears and because large muscle groups are used a large amount of tears will occur. This muscle damage needs to be repaired and will take between 48 and 72 hours. This process uses energy therefore again leading to more calories been burnt in this period hence increasing the afterburn even further!

Here is an eaxmple of a great HIIT workout involving body weight resistance exercises.

Burpees - 20 seconds
Tuck jumps - 20 seconds
Press ups - 20 seconds
High knees running - 20 seconds
Squat jumps - 20 seconds

All exercises 20 seconds, with 20 seconds rest, aim for 3-4 sets to start with increasing to 5 in time.

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